[Technical Field]
[0001] The present disclosure relates to a base station device, a radio communication device,
and a radio communication system.
[Background Art]
[0002] Radio access methods and radio networks for cellular mobile communication (hereinafter,
also referred to as "Long Term Evolution (LTE)", "LTE-Advanced (LTE-A)", "LTE-Advanced
Pro (LTE-APro)", "New Radio (NR)", "New Radio Access Technology (NRAT)", "Evolved
Universal Terrestrial Radio Access (EUTRA)", or "Further EUTRA (FEUTRA)") are considered
in the 3rd Generation Partnership Project (3GPP). Note that, in the following description,
LTE includes LTE-A, LTE-A Pro, and EUTRA, and NR includes NRAT and FEUTRA. In LTE,
a base station device (base station) is also referred to as an evolved NodeB (eNodeB).
In NR, a base station device is also referred to as a gNodeB. In addition, in NR,
a terminal device (mobile station, mobile station device, and terminal) is also referred
to as user equipment (UE). LTE and NR are cellular communication systems in which
a plurality of areas covered by a base station device is arranged in a cell form.
A single base station device may manage a plurality of cells.
[0003] NR is a radio access technology (RAT) different from LTE as a next-generation radio
access method for LTE. NR is an access technology that can cope with various use cases
including enhanced mobile broadband (eMBB), massive machine type communications (mMTC),
and ultra-reliable and low-latency communications (URLLC). NR is studied aiming at
a technical framework corresponding to use scenarios, request conditions, arrangement
scenarios, and the like in those use cases.
[0004] In recent years, support for high-frequency bands such as millimeter waves and terahertz
waves and cost reduction of base stations have been required, and a reduction in the
Peak-To-Average-Power-Ratio (PAPR) in the downlink is required. In addition, small
satellites (for example, they may be referred to as Cube-sats, micro-satellites, and
the like) that are considered as mobile satellites are inferior to conventional satellites
in terms of power or antenna gain. Thus, there is a problem in that it is difficult
to meet the requirement of low PAPR because they do not have high-performance power
amplifiers. Disclosure regarding communication waveforms in uplink is described in
PTL 1, disclosure regarding communication waveforms in downlink is described in PTL
2, and disclosure regarding satellites is described in NPL 1.
[Citation List]
[Patent Literature]
[Non Patent Literature]
[Summary]
[Technical Problem]
[0007] The present disclosure proposes a base station device, a terminal device, and a radio
communication system that make it possible to meet the requirement of low PAPR in
downlink communication.
[Solution to Problem]
[0008] Abase station device of the present disclosure includes a controller configured to:
notify a terminal device of first information regarding a signal waveform to be used
in downlink communication in an initial connection procedure performed with the terminal
device among a first signal waveform and a second signal waveform; and perform the
downlink communication with the signal waveform to be used based on the first information.
[Brief Description of Drawings]
[0009]
[Fig. 1]
Fig. 1 is a diagram showing an example of an outline of a terrestrial network and
a non-terrestrial network.
[Fig. 2]
Fig. 2 is a diagram showing an example of an outline of a geostationary satellite
and a low-earth-orbiting satellite.
[Fig. 3]
Fig. 3 is a diagram showing an example of a cell configured by a low-earth-orbiting
satellite.
[Fig. 4]
Fig. 4 is a diagram for explaining an outline of a communication system according
to an embodiment of the present disclosure.
[Fig. 5]
Fig. 5 is a block diagram of a base station device according to an embodiment of the
present disclosure.
[Fig. 6]
Fig. 6 is a block diagram of a radio transmitter in the base station device.
[Fig. 7]
Fig. 7 is a block diagram of a first signal waveform transmitter in the base station
device.
[Fig. 8]
Fig. 8 is a block diagram of a second signal waveform transmitter in the base station
device.
[Fig. 9]
Fig. 9 is a block diagram of a terminal device according to an embodiment of the present
disclosure.
[Fig. 10]
Fig. 10 is a block diagram of a radio receiver in the terminal device.
[Fig. 11]
Fig. 11 is a block diagram of a first signal waveform receiver in the terminal device.
[Fig. 12]
Fig. 12 is a block diagram of a second signal waveform receiver in the terminal device.
[Fig. 13]
Fig. 13 is a diagram showing an example of an NR frame structure as a radio frame
structure.
[Fig. 14]
Fig. 14 is a diagram showing signal processing on the transmitting side and receiving
side during 5G NR downlink or uplink transmission.
[Fig. 15]
Fig. 15 is a diagram showing an example of an initial connection procedure for a terminal
device.
[Fig. 16]
Fig. 16 is a diagram showing an example of a contention-based RACH procedure.
[Fig. 17]
Fig. 17 is a diagram showing an example of a non-contention-based RACH procedure.
[Fig. 18]
Fig. 18 is a sequence diagram showing an example of the NR 2-step RACH procedure.
[Fig. 19]
Fig. 19 is a sequence diagram showing an example of the flow of communication processing
according to the embodiment of the present disclosure.
[Fig. 20]
Fig. 20 is a diagram showing an example of contiguous resource allocation in the frequency
domain when performing single-carrier transmission on the uplink.
[Fig. 21]
Fig. 21 is a diagram showing an example of discontiguous resource allocation in the
frequency domain when performing single-carrier transmission on the uplink.
[Fig. 22]
Fig. 22 is a diagram showing a configuration example of a second signal waveform transmitter
in the base station device.
[Fig. 23]
Fig. 23 is a diagram showing another configuration example of the second signal waveform
transmitter in the base station device.
[Fig. 24]
Fig. 24 is a diagram showing still another configuration example of the second signal
waveform transmitter in the base station device.
[Fig. 25]
Fig. 25 is a diagram showing still another configuration example of the second signal
waveform transmitter in the base station device.
[Description of Embodiments]
[0010] Hereinafter, embodiments of the present disclosure will be described with reference
to the drawings. In one or more embodiments shown in the present disclosure, the elements
included in each embodiment can be combined with each other, and the combined result
is also part of the embodiments shown in the present disclosure.
[0011] As described in Background Art, a reduction in the Peak-To-Average-Power Ratio (PAPR)
in the downlink is required. A transmission method using a single-carrier signal (single-carrier
transmission method) is effective for reducing PAPR. An example of a single-carrier
transmission method is DFT-Spread-OFDM. On the other hand, a transmission method using
multi-carrier signals (multi-carrier transmission method) is effective in multi-layer
transmission (MIMO transmission). OFDM is an example of a multi-carrier transmission
method. It is necessary to support two transmission methods or signal waveforms in
the downlink: multi-carrier transmission and single-carrier transmission.
[0012] For example, when supporting both multi-carrier transmission and single-carrier
transmission, during the initial connection procedure (also referred to as initial
access procedure) that a terminal device performs with a base station device, there
is an issue of which transmission method to apply, multi-carrier transmission or single-carrier
transmission.
[0013] As a related technique, there is a method in which a single-carrier signal is used
in a high-frequency band such as millimeter waves or terahertz waves, and a multi-carrier
signal is used in a low-frequency band. One of the reasons why this method is not
suitable for multi-layer transmission is that a reduction in PAPR in higher frequency
bands is more required than in lower frequency bands, and that radio waves travel
in a straight line in high-frequency bands and thus the number of radio wave propagation
paths in high-frequency bands is smaller than in low-frequency bands.
[0014] However, even in low-frequency bands, PAPR reduction is required depending on the
performance of a base station device. Even in high-frequency bands, there are cases
where it is desired to perform multi-layer transmission by artificially increasing
the number of radio wave propagation paths. Therefore, the present embodiment proposes
a method that enables both of these cases to be handled by properly using both single-carrier
signals that can reduce PAPR and multi-carrier signals that are suitable for multi-layer
transmission regardless of the frequency band.
[0015] Furthermore, as a related technique, single-carrier transmission is performed in
the uplink, and in this case, it is necessary to allocate contiguous resources in
the frequency domain. The reason for this is that PAPR increases unless resources
are allocated contiguously in the frequency domain. In this case, if the communication
quality of consecutive resources is poor, high-speed communication cannot be achieved.
Even when single-carrier transmission is performed on the downlink, a similar problem
may occur if there is a constraint on allocating consecutive resources to terminal
devices. The present embodiment proposes a method that enables discontiguous resource
allocation in the frequency domain while suppressing an increase in PAPR. More flexible
resource allocation becomes possible, and the speed and capacity of downlink communication
can be further increased.
[0016] Below, first, prior knowledge regarding the embodiments of the present disclosure
will be described.
<Terrestrial network and non-terrestrial network>
[0017] Fig. 1 shows an example of an outline of a terrestrial network and a non-terrestrial
network.
[0018] In cellular mobile communications, a cell (macro cell 17, micro cell, femto cell
18, or small cell) is made up of a base station device 1 (for example, eNodeB (eNB),
gNodeB (gNB), RAN node (including EUTRAN, NGRAN)) or a relay device 3 installed on
the ground, and a radio network is made up of a plurality of cells. The base station
device 1 or the relay device 3 may be referred to as a ground station device. A radio
network composed of and provided by ground station devices is referred to as a terrestrial
network 4.
[0019] On the other hand, due to demands such as reducing the cost of base station devices
and providing coverage to areas where radio waves are difficult to reach from base
station devices, provision of a radio network configured by communication devices
floating in the air, such as, satellites orbiting the earth (satellite base station
devices, satellite relay station devices, space stations), aerial vehicles, and drones,
is being considered. A radio network composed of communication devices other than
ground stations is referred to as a non-terrestrial network (NTN).
[0020] Examples of communication devices other than ground stations include satellite devices
and aviation station devices. A satellite device is a device such as an artificial
satellite that floats outside the atmosphere and has a radio communication function.
The satellite devices in the present embodiment include a low earth orbiting (LEO)
satellite 12, a medium earth orbiting (MEO) satellite, a geostationary earth orbiting
(GEO) satellite 11, and a highly elliptical orbiting (HEO) satellites. The aviation
station device 13 is a device such as an aircraft or a balloon that floats in the
atmosphere and has a radio communication function. The aviation station device 13
in the present embodiment includes an airborne platform 19, specifically, for example,
an unmanned aircraft system (UAS), a tethered unmanned aircraft system (UAS), a light
unmanned aircraft system (Lighter than Air UAS, LTA), a heavy unmanned aircraft system
(Heavier than Air UAS, HTA), and a high altitude unmanned aircraft system (High Altitude
UAS Platform, HAP). Note that communication devices other than ground stations may
also be referred to as "eNodeB (eNB), gNodeB (gNB), RAN node (including EUTRAN, NGRAN)"
from the perspective of cellular mobile communications based on 3GPP.
[0021] The satellite devices 11 and 12 and the aviation station device 13 are connected
to a terrestrial network (core network, for example, EPC or 5GC) via the relay station
3 installed on the earth. The core network 15 is connected to a wide area network
such as the Internet 16. Hereinafter, the relay station 3 may be referred to as an
earth station (very small aperture terminal, gateway, control earth station, HUB station).
A terminal device 2 (UE: User Equipment) corresponding to a non-terrestrial network
communicates with these satellite devices 11 and 12 and/or the aviation station device
13. Terminal devices (terrestrial terminal devices) compatible with non-terrestrial
networks include mobile phones, smartphones, cars, buses, trains, aircrafts, M2M (Machine
to Machine)/IoT (Internet of Things) devices, relay stations for relaying satellite
communications, and base stations for receiving satellite communications.
<Satellite communication>
[0022] Satellite communication refers to radio communication between a satellite device
and a terminal device. Satellite device is mainly divided into geostationary satellites
and low-earth-orbiting satellites.
[0023] Fig. 2 shows an example of an outline of the geostationary satellite 11 and the low-earth-orbiting
satellite 12. The geostationary satellite 11 is located at an altitude of approximately
35,786 km and revolves around the earth at the same speed as the earth's rotation
speed. The geostationary satellite 11 is a satellite whose relative speed with respect
to the terminal device 2 on the ground is approximately 0, and is observed from the
terminal device 2 on the ground as if it were stationary. The low-earth-orbiting satellite
12 is generally located at an altitude of 100 km and 2000 km, and is a satellite that
orbits at a lower altitude than other satellites. Unlike the geostationary satellite
11, the low-earth-orbiting satellite 12 has a relative speed with respect to the terminal
device 2 on the ground, and is observed from the terminal device 2 on the ground as
if it were moving.
[0024] Fig. 3 is an example of a cell configured by the low-earth-orbiting satellite 12.
A satellite orbiting in a low orbit communicates with a terminal device on the ground
while having a predetermined directivity on the ground. The low-earth-orbiting satellite
12 is moving at a constant speed. When it becomes difficult for a certain low-earth-orbiting
satellite 12 to provide satellite communication to a terminal device on the ground,
a subsequent low-earth-orbiting satellite (neighbor satellite station) provides satellite
communication to the terminal device on the ground (that is, it is assumed that there
is connected mobility).
[0025] As mentioned above, medium-earth-orbiting satellites and low-earth-orbiting satellites
12 move in orbit at very high speeds in the sky. For example, in the case of low-earth-orbiting
satellites at an altitude of 600 km, they move in orbit at a speed of 7.6 km/s. The
low-earth-orbiting satellite 12 forms a cell (or beam) on the ground with a radius
of several tens of kilometers to several hundred kilometers. However, since the cells
formed on the ground also move with the movement of a satellite, the terminal device
on the ground may need to perform handover even if the terminal device is not moving.
For example, assuming a case where the cell diameter formed on the ground is 50 km
and the ground terminal device is not moving, handover occurs in about 6 to 7 seconds.
Note that the numerical values shown in the figures are just examples, and the present
invention is not limited to these numerical values.
[0026] Non-terrestrial networks are expected to provide the following services:
- Extension of services to terminal devices (mainly IoT devices/MTC, public safety/critical
communications) in areas that cannot be covered by terrestrial networks (for example,
outside of cell coverage)
- Service reliability and resiliency to reduce service vulnerability to physical attacks
or natural disasters
- Connection and provision of services to airplane passengers and aircraft terminals
such as drones (for example, Aerial UE(s))
- Connection and provision of services to mobile terminals such as ships and trains
- Provision of highly efficient multicast/broadcast services such as A/V content, group
communications, IoT broadcast services, software downloads, and emergency messages
- Traffic offloading of communications between terrestrial and non-terrestrial networks
[0027] In addition to terrestrial base station devices, the base station device in the following
description may include non-terrestrial base station devices that operate as communication
devices, such as satellites, drones, balloons, and airplanes.
[0028] In the following description, when a specific example is shown, if there is a place
where a specific value is shown and explained, the value is not limited to that example,
and another value may be used.
[0029] The resources described in the following description include at least one of frequency,
time, resource element (including REG, CCE, CORESET), resource block, bandwidth part
(BWP), component carrier, symbol, sub-symbol, slot, mini-slot, subslot, subframe,
frame, PRACH occasion, occasion, code, multi-access physical resource, multi-access
signature, subcarrier spacing (Numerology), and the like.
<Outline of communication system>
[0030] Fig. 4 is a diagram for explaining an outline of a communication system according
to an embodiment of the present disclosure. The communication system in Fig. 4 includes
a base station device 1 and a plurality of terminal devices 2A and 2B. Hereinafter,
when the terminal devices 2A and 2B are not particularly distinguished, they will
be referred to as the terminal device 2, and the terminal device 2 may be either the
terminal device 2A or 2B.
[0031] The base station device 1 determines a signal waveform used for downlink communication
with the terminal device 2 (for example, a signal waveform to be used in the initial
connection with the terminal device 2). For example, the base station device 1 determines
to use either a single-carrier signal or a multi-carrier signal for downlink communication.
Examples of multi-carrier signals include OFDM signals and CP-OFDM signals. Examples
of single-carrier signals include a DFT-S-OFDM signal (SC-FDMA signal), an SC-QAM
signal, and a single-carrier with zero padding/unique word. Details of these signals
will be described later.
[0032] The base station device 1 determines a signal waveform to be used for each terminal
device 2, for example, and notifies the terminal device 2 of information regarding
the determined signal waveform. The base station device 1 performs downlink communication
with the terminal device 2 using the notified signal waveform. As an example, the
base station device 1 determines a single-carrier signal for downlink communication
where low PAPR is strictly required, and determines a signal waveform other than the
single-carrier signal (here, the multi-carrier signal) for downlink communication
where low PAPR is not so strictly required. Accordingly, the base station device 1
can achieve low PAPR and improve the efficiency of the entire system.
[0033] In the example of Fig. 4, the base station device 1 selects a multi-carrier signal
and performs downlink communication S1 with respect to the terminal device 2A located
closer to the center of the cell C. This is because the required transmission power
for the terminal device 2A located closer to the center of the cell C is smaller than
that for the cell edge, making it easier to secure the necessary transmission power
even if the PAPR is high. Furthermore, the base station device 1 selects a single-carrier
signal and performs downlink communication S2 with respect to the terminal device
2B located closer to the edge of the cell C. This is because larger transmission power
is required and low PAPR is required in order to perform downlink communication with
the terminal device 2B located closer to the cell edge.
[0034] Although an example has been described in which the base station device 1 determines
the signal waveform according to the position of the terminal device 2 in the cell
C, the method by which the base station device 1 determines the signal waveform is
not limited to this. Details of how the base station device 1 determines the signal
waveform will be described later.
<Configuration example of base station device>
[0035] Fig. 5 is a block diagram of the base station device 1 according to the embodiment
of the present disclosure. The base station device 1 includes an upper-layer processor
101, a controller 103, a receiver 105, a transmitter 107, and an antenna 109. The
controller 103 is a first controller that performs control on the base station device
1 side.
[0036] The base station device 1 may support one or more RATs (Radio Access Technologies).
For example, base station device 1 may support both LTE and NR. In this case, some
or all of the units included in the base station device 1 may be configured individually
depending on the RAT. For example, the receiver 105 and the transmitter 107 are configured
individually for LTE and NR. In addition, in the NR cell, some or all of the units
included in the base station device 1 may be individually configured according to
a parameter set regarding a transmission signal. For example, in a certain NR cell,
a radio receiver 1057 and a radio transmitter 1077 may be individually configured
according to a parameter set regarding a transmission signal.
[0037] The upper-layer processor 101 outputs downlink data (transport block) to the controller
103. The upper-layer processor 101 performs processing of a medium access control
(MAC) layer, a packet data convergence protocol (PDCP) layer, a radio link control
(RLC) layer, a radio resource control (RRC) layer. In addition, the upper-layer processor
101 generates control information for controlling the receiver 105 and the transmitter
107, and outputs the generated control information to the controller 103.
[0038] The upper-layer processor 101 performs processing and management regarding RAT control,
radio resource control, subframe structure, scheduling control, and/or CSI reporting
control. Processing and management in the upper-layer processor 101 are performed
for each terminal device or in common for all terminal devices connected to the base
station device. Processing and management in the upper-layer processor 101 may be
performed individually depending on the RAT. For example, the upper-layer processor
101 individually performs processing and management in LTE and processing and management
in NR.
[0039] In the RAT control in the upper-layer processor 101, management regarding the RAT
is performed. For example, in RAT control, management regarding LTE and/or management
regarding NR is performed. Management regarding NR includes the setting and processing
of parameter sets regarding transmission signals in NR cells.
[0040] In the radio resource control in the upper-layer processor 101, configuration information
in the subject device is managed. Radio resource control in the upper-layer processor
101 involves the generation and/or management of downlink data (transport blocks),
system information, RRC messages (RRC parameters), and/or MAC control elements (CE).
[0041] Subframe settings in the upper-layer processor 101 involve the management of subframe
settings, subframe pattern settings, uplink downlink settings, uplink reference UL-DL
settings, and/or downlink reference UL-DL settings. Note that the subframe settings
in the upper-layer processor 101 are also referred to as base station subframe settings.
Furthermore, the subframe settings in the upper-layer processor 101 can be determined
based on the uplink traffic amount and the downlink traffic amount. Furthermore, the
subframe settings in the upper-layer processor 101 can be determined based on the
scheduling result of the scheduling control in the upper-layer processor 101.
[0042] In the scheduling control in upper-layer processor 101, the frequency and subframe
to which a physical channel is allocated and physical channel coding rate, modulation
method, transmission power, and the like are determined based on the channel state
information received from the terminal device and the propagation path estimation
value or channel quality input from a channel measurement unit 1059. For example,
the controller 103 generates control information (DCI format) based on the scheduling
result of the scheduling control in the upper-layer processor 101.
[0043] In the CSI reporting control in the upper-layer processor 101, CSI reporting of the
terminal device 2 is controlled. For example, settings regarding CSI reference resources
assumed for calculating CSI in the terminal device 2 are controlled.
[0044] The controller 103 controls the receiver 105 and the transmitter 107 based on the
control information from the upper-layer processor 101. The controller 103 generates
control information for the upper-layer processor 101 and outputs it to the upper-layer
processor 101. The controller 103 receives the decoded signal from a decoder 1051
and the channel estimation result from the channel measurement unit 1059. The controller
103 outputs a signal to be encoded to an encoder 1071. The controller 103 is used
to control all or part of the base station device 1.
[0045] The controller 103 determines a signal waveform (hereinafter also referred to as
a signal waveform to be used) to be used for downlink communication with the terminal
device 2 from among the single-carrier signal and the multi-carrier signal. The controller
103 controls the transmitter 107 to notify the terminal device 2 of information regarding
the signal waveform to be used using a predetermined signal waveform (for example,
a single-carrier signal). In addition, the controller 103 controls the transmitter
107 to perform downlink communication with the terminal device 2 using the notified
signal waveform to be used.
[0046] The receiver 105 receives the signal transmitted from the terminal device 2 via the
antenna 109 under the control of the controller 103, performs reception processing
such as separation, demodulation, and decoding, and outputs the received information
to the controller 103. Note that the reception processing in the receiver 105 is performed
based on predefined settings or settings notified to the terminal device 2 by the
base station device 1. The receiver 105 includes a decoder 1051, a demodulator 1053,
a demultiplexer 1055, a radio receiver 1057, and a channel measurement unit 1059.
[0047] The radio receiver 1057 performs, on the uplink signal received via the antenna 109,
conversion to an intermediate frequency (downconversion), removal of unnecessary frequency
components, control of amplification level to maintain an appropriate signal level,
orthogonal demodulation based on the in-phase and orthogonal components of the received
signal, analog-to-digital conversion of signals, removal of guard interval (GI), and/or
extraction of frequency domain signals by fast Fourier transform (FFT).
[0048] The demultiplexer 1055 separates an uplink channel such as PUCCH or PUSCH and/or
an uplink reference signal from the signal input from the radio receiver 1057. The
demultiplexer 1055 outputs the uplink reference signal to the channel measurement
unit 1059. The demultiplexer 1055 performs propagation path compensation for the uplink
channel based on the propagation path estimation value input from the channel measurement
unit 1059.
[0049] The demodulator 1053 performs BPSK (Binary Phase Shift Keying), n/2 BPSK, QPSK (Quadrature
Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM, 256QAM, and the
like to demodulate the received signal. Furthermore, the demodulator 1053 performs
separation and demodulation of MIMO-multiplexed uplink channels.
[0050] The decoder 1051 performs decoding processing on the encoded bits of the demodulated
uplink channel. The decoded uplink data and/or uplink control information is output
to the controller 103. The decoder 1051 performs decoding processing for each transport
block for PUSCH.
[0051] The channel measurement unit 1059 measures the propagation path estimation value
and/or channel quality from the uplink reference signal input from the demultiplexer
1055 and outputs it to the demultiplexer 1055 and/or the controller 103. For example,
the channel measurement unit 1059 measures the propagation path estimation value for
performing propagation path compensation for PUCCH or PUSCH using UL-DMRS, and measures
the quality of the channel in the uplink using SRS (Sounding Reference Signal).
[0052] The transmitter 107 performs transmission processing such as encoding, modulation,
and multiplexing on downlink control information and downlink data input from the
upper-layer processor 101 under the control of the controller 103. For example, the
transmitter 107 generates and multiplexes PHICH, PDCCH, EPDCCH, PDSCH, and downlink
reference signals, and generates a transmission signal. Note that the transmission
processing in the transmitter 107 is based on predefined settings, settings notified
by the base station device 1 to the terminal device 2, or settings notified through
the PDCCH or EPDCCH transmitted in the same subframe. The transmitter 107 includes
an encoder 1071, a modulator 1073, a multiplexer 1075, a radio transmitter 1077, and
a downlink reference signal generator 1079.
[0053] The encoder 1071 encodes the HARQ indicator (HARQ-ACK), downlink control information,
and downlink data input from the controller 103 using an encoding method such as block
encoding, convolutional encoding, or turbo encoding. The modulator 1073 modulates
the encoded bits input from the encoder 1071 using a modulation method such as BPSK,
n/2 BPSK, QPSK, 16QAM, 64QAM, or 256QAM. The downlink reference signal generator 1079
generates a downlink reference signal based on a physical cell identification (PCI),
RRC parameters set in the terminal device 2, and the like.
[0054] The multiplexer 1075 multiplexes the modulation symbol of each channel and the downlink
reference signal, and arranges it in a predetermined resource element.
[0055] The radio transmitter 1077 performs processing on the signal from the multiplexer
1075, such as conversion of signals using at least the latter of DFT and IDFT, addition
of guard intervals, generation of baseband digital signals, conversion to analog signals,
orthogonal modulation, conversion (upconversion) from an intermediate frequency signal
to a high-frequency signal, removal of extra frequency components, and amplification
of power and generates a transmission signal. The transmission signal output by the
radio transmitter 1077 is transmitted from the antenna 109.
[0056] The radio transmitter 1077 can support a plurality of signal waveforms (downlink
signal waveforms) in the downlink. Details of the radio transmitter 1077 in the base
station device 1 that supports both the first signal waveform and the second signal
waveform will be explained using Figs. 6 to 8. In the following explanation, it is
assumed that the first signal waveform includes a multi-carrier signal and the second
signal waveform includes a single-carrier signal. However, a case where the first
signal waveform includes a single-carrier signal and the second signal waveform includes
a multi-carrier signal is not excluded.
[0057] Fig. 6 is a block diagram of the radio transmitter 1077. The radio transmitter 1077
includes a signal waveform switch 401, a first signal waveform transmitter 403, and
a second signal waveform transmitter 405.
[0058] The signal waveform switch 401 (signal waveform controller) determines whether to
use the first signal waveform or the second signal waveform in downlink communication
depending on conditions or situations, and switches the output destination of the
signal input from the multiplexer 1075 according to the result of the determination.
When using the first signal waveform, the first signal waveform transmitter 403 is
the output destination, and downlink transmission processing is performed by the first
signal waveform transmitter 403. When using the second signal waveform, the second
signal waveform transmitter 405 is the output destination, and downlink transmission
processing is performed by the second signal waveform transmitter 405. Conditions
or situations for switching in the signal waveform switch 401 will be described later.
In Fig. 6, the first signal waveform transmitter 403 and the second signal waveform
transmitter 405 are described as different processors, but they may be treated as
one processor and the transmission processing may be switched.
[0059] Fig. 7 is a block diagram of the first signal waveform transmitter 403. The first
signal waveform transmitter 403 performs transmission processing on a multi-carrier
signal (here, a downlink channel and signal transmitted by CP-OFDM) as a signal waveform
of downlink communication. The first signal waveform transmitter 403 includes an S/P
(Serial/Parallel) unit 4031, an IDFT (Inverse Discrete Fourier Transform) unit 4033,
a P/S (Parallel/Serial) unit 4035, and a CP inserter 4037.
[0060] The S/P unit 4031 converts the input serial signal into a parallel signal of size
M. The size M is determined depending on the size of frequency domain resources used
for downlink communication. The parallel signal of size M is input to the IDFT unit
4033 so as to correspond to a predetermined frequency domain.
[0061] The IDFT unit 4033 performs inverse Fourier transform processing on the parallel
signal of size N. When the size N is an exponent of 2, the Fourier transform processing
may be IFFT (Inverse Fast Fourier Transform) processing. The P/S unit 4035 converts
a parallel signal of size N into a serial signal. The CP inserter 4037 inserts a CP
for each OFDM symbol.
[0062] Fig. 8 is a block diagram of the second signal waveform transmitter 405. The second
signal waveform transmitter 405 performs transmission processing on a single-carrier
signal (here, a downlink channel and signal transmitted by SC-FDMA) as a signal waveform
of downlink communication. The second signal waveform transmitter 405 uses DFT-Spread-OFDM
for transmission processing. The second signal waveform transmitter 405 includes a
DFT unit 4051, an IDFT (Inverse Discrete Fourier Transform) unit 4053, a P/S unit
4055, and a CP inserter 4057. The DFT unit 4051 performs inverse Fourier transform
(DFT) on the input serial signal into a parallel signal of size M. The size M is determined
depending on the size of frequency domain resources used for downlink communication.
The parallel signal of size M is input to the IDFT unit 4053 so as to correspond to
a predetermined frequency domain. The IDFT unit 4053 performs inverse Fourier transform
processing on the parallel signal of size N. When the size N is an exponent of 2,
the inverse Fourier transform processing may be IFFT (Inverse Fast Fourier Transform)
processing. The P/S unit 4055 converts a parallel signal of size N into a serial signal.
The CP inserter 4057 inserts a CP for each SC-FDMA symbol or for each DFT-Spread-OFDM
symbol.
[0063] Fig. 9 is a block diagram of the terminal device 2 according to the embodiment of
the present disclosure. The terminal device 2 in Fig. 9 includes an upper-layer processor
201, a controller 203, a receiver 205, a transmitter 207, and an antenna 209. The
controller 203 is a second controller that performs control on the terminal device
2 side.
[0064] The terminal device 2 may support one or more RATs (Radio Access Technologies). For
example, the terminal device 2 may support both LTE and NR. In this case, some or
all of the units included in the terminal device 2 may be configured individually
depending on the RAT. For example, the receiver 205 and the transmitter 207 are configured
individually for LTE and NR. In addition, in the NR cell, some or all of the units
included in the terminal device 2 shown in Fig. 9 may be individually configured according
to the parameter set regarding the transmission signal. For example, in a certain
NR cell, the radio receiver 2057 and the radio transmitter 2077 may be individually
configured according to a parameter set regarding the transmission signal.
[0065] The upper-layer processor 201 outputs uplink data (transport block) to the controller
203. The upper-layer processor 201 performs processing of a medium access control
(MAC) layer, a packet data convergence protocol (PDCP) layer, a radio link control
(RLC) layer, and a radio resource control (RRC) layer. In addition, the upper-layer
processor 201 generates control information to control the receiver 205 and the transmitter
207 and outputs it to the controller 203.
[0066] The upper-layer processor 201 performs processing and management regarding RAT control,
radio resource control, subframe structure, scheduling control, and/or CSI reporting
control. Processing and management in the upper-layer processor 201 are performed
based on predefined settings and/or settings based on control information set or notified
from the base station device 1. For example, the control information from the base
station device 1 includes RRC parameters, MAC control elements, or DCI. Furthermore,
the processing and management in the upper-layer processor 201 may be performed individually
depending on the RAT. For example, the upper-layer processor 201 separately performs
processing and management in LTE and processing and management in NR.
[0067] In the RAT control in the upper-layer processor 201, management regarding the RAT
is performed. For example, in RAT control, management regarding LTE and/or management
regarding NR is performed. Management regarding NR includes the setting and processing
of parameter sets regarding transmission signals in NR cells.
[0068] In the radio resource control in the upper-layer processor 201, configuration information
in the subject device is managed. Radio resource control in the upper-layer processor
201 involves the generation and/or management of uplink data (transport blocks), system
information, RRC messages (RRC parameters), and/or MAC control elements (CEs).
[0069] The upper-layer processor 201 manages subframe settings in the base station device
1 and/or another base station device different from the base station device 1. The
subframe settings include uplink or downlink settings for the subframe, subframe pattern
settings, uplink downlink settings, uplink reference UL-DL settings, and/or downlink
reference UL-DL settings. The subframe setting in the upper-layer processor 201 is
also referred to as terminal device subframe setting.
[0070] In the scheduling control in the upper-layer processor 201, control information for
controlling the scheduling of the receiver 205 and the transmitter 207 is generated
based on DCI (scheduling information) from the base station device 1.
[0071] In the CSI reporting control in the upper-layer processor 201, control regarding
reporting of CSI to the base station device 1 is performed. For example, in CSI reporting
control, settings regarding CSI reference resources assumed for calculating CSI in
the channel measurement unit 2059 are controlled. The CSI reporting control involves
controlling resources (timings) used to report CSI based on DCI and/or RRC parameters.
[0072] The controller 203 controls the receiver 205 and the transmitter 207 based on control
information from the upper-layer processor 201. The controller 203 generates control
information for the upper-layer processor 201 and outputs it to the upper-layer processor
201. The controller 203 receives the decoded signal from the decoder 2051 and the
channel estimation result from the channel measurement unit 2059. The controller 203
outputs a signal to be encoded to the encoder 2071. In addition, the controller 203
may be used to control all or part of the terminal device 2.
[0073] The controller 203 acquires information regarding the signal waveform (signal waveform
to be used) used for downlink communication with the base station device 1 from the
base station device 1 through the receiver 205 among the single-carrier signal and
the multi-carrier signal. Information regarding the signal waveform to be used may
be transmitted in association with a predetermined signal. The predetermined signal
may be transmitted with a predetermined signal waveform among a single-carrier signal
and a multi-carrier signal. The controller 203 controls the receiver 205 to perform
downlink communication with the base station device 1 using the reception processing
for the signal waveform to be used.
[0074] The receiver 205 receives the signal transmitted from the base station device 1 via
the antenna 209 under the control of the controller 203, further performs reception
processing such as separation, demodulation, and decoding, and outputs the received
information to the controller 203. Note that the reception processing in the receiver
205 is performed based on predefined settings or notifications or settings from the
base station device 1. The receiver 205 includes a decoder 2051, a demodulator 2053,
a demultiplexer 2055, a radio receiver 2057, and a channel measurement unit 2059.
[0075] The radio receiver 2057 performs processing on the uplink signal received via the
antenna 209 such as conversion (downconversion) into an intermediate frequency, removal
of unnecessary frequency components, control of an amplification level to maintain
an appropriate signal level, orthogonal demodulation based on in-phase and orthogonal
components of received signals, conversion from analog signals to digital signals,
removal of guard interval (GI), and/or extraction of frequency domain signals by fast
Fourier transform (FFT).
[0076] The radio receiver 2057 can support a plurality of downlink signal waveforms (first
signal waveform and second signal waveform). Details of the radio receiver 2057 in
the terminal device 2 that supports both the first signal waveform and the second
signal waveform will be described using Figs. 10 to 12.
[0077] Fig. 10 is a block diagram of the radio receiver 2057. The radio receiver 2057 includes
a signal waveform switch 301, a first signal waveform receiver 303, and a second signal
waveform receiver 305.
[0078] The signal waveform switch 301 (signal waveform controller) determines whether the
received downlink communication signal has a first signal waveform or a second signal
waveform depending on the condition or situation, and switches the signal output destination
according to the determination result. When the downlink communication signal has
the first signal waveform, the downlink communication signal is received by the first
signal waveform receiver 303. The reception processing performed by the first signal
waveform receiver 303 is reception processing for the first signal waveform. When
the downlink communication signal has the second signal waveform, the downlink communication
signal is received by the second signal waveform receiver 305. The reception processing
performed by the second signal waveform receiver 305 is reception processing for the
second signal waveform. Conditions or situations for switching in the signal waveform
switch 301 will be described later. In Fig. 10, the first signal waveform receiver
303 and the second signal waveform receiver 305 are described as different processors,
but they may be treated as one processor and only a part of the reception processing
may be performed by switching.
[0079] Fig. 11 is a block diagram of the first signal waveform receiver 303. The first signal
waveform receiver 303 performs reception processing on a multi-carrier signal (here,
a downlink channel and signal transmitted by CP-OFDM) as a signal waveform of downlink
communication. The first signal waveform receiver 303 includes a CP remover 3031,
an S/P unit 3033, a DFT (Discrete Fourier Transform) unit 3035, and a P/S unit 3037.
[0080] The CP remover 3031 removes a CP (cyclic prefix) from the received downlink communication
signal. The S/P unit 3033 converts the input serial signal into a parallel signal
of size N. The DFT unit 3035 performs Fourier transform processing on the parallel
signal of size N and outputs a parallel signal of size N. When the size N is an exponent
of 2, the Fourier transform processing may be FFT (Fast Fourier Transform) processing.
The P/S unit 3037 converts the input parallel signal of size M into a serial signal.
The size M is determined depending on the size of frequency domain resources used
for downlink communication. A downlink communication signal transmitted by the base
station device 1 that performs transmission processing is input to the IDFT 3037.
[0081] Fig. 12 is a block diagram of the second signal waveform receiver 305. The second
signal waveform receiver 305 performs reception processing on a single-carrier signal
(here, a downlink channel and signal transmitted by SC-FDMA) as a signal waveform
of downlink communication. The second signal waveform receiver 305 includes a CP remover
3051, an S/P unit 3053, a DFT (Discrete Fourier Transform) unit 3055, and an IDFT
(Inverse Discrete Fourier Transform) unit 3057.
[0082] The CP remover 3051 removes a CP (cyclic prefix) from the received downlink communication
signal and outputs a serial signal. The S/P unit 3053 converts the input serial signal
into a parallel signal of size N. The DFT unit 3055 performs Fourier transform processing
on the parallel signal of size N. When the size N is an exponent of 2, the Fourier
transform processing may be FFT (Fast Fourier Transform) processing. The IDFT unit
3057 performs inverse Fourier transform processing on the input signal of size M.
The size M is determined depending on the size of frequency domain resources used
for downlink communication. A downlink communication signal transmitted by the base
station device 1 that performs transmission processing is input to the IDFT 3057.
[0083] The demultiplexer 2055 in Fig. 9 separates a downlink channel such as PHICH, PDCCH,
EPDCCH, or PDSCH, a downlink synchronization signal, and/or a downlink reference signal
from the signal input from the radio receiver 2057. The demultiplexer 2055 outputs
the downlink reference signal to the channel measurement unit 2059. The demultiplexer
2055 performs propagation path compensation for the downlink channel from the propagation
path estimation value input from the channel measurement unit 2059.
[0084] The demodulator 2053 demodulates the received signal using a modulation method such
as BPSK, n/2 BPSK, QPSK, 16QAM, 64QAM, or 256QAM on the modulation symbol of the downlink
channel. The demodulator 2053 performs separation and demodulation of MIMO multiplexed
downlink channels.
[0085] The decoder 2051 performs decoding processing on the encoded bits of the demodulated
downlink channel. The decoded downlink data and/or downlink control information is
output to the controller 203. The decoder 2051 performs decoding processing for each
transport block on the PDSCH.
[0086] The channel measurement unit 2059 measures a propagation path estimation value and/or
channel quality from the downlink reference signal input from the demultiplexer 2055
and outputs it to the demultiplexer 2055 and/or the controller 203. The downlink reference
signal used for measurement by the channel measurement unit 2059 may be determined
based on at least the transmission mode set by RRC parameters and/or other RRC parameters.
For example, DL-DMRS is used for measuring a propagation path estimation value for
performing propagation path compensation for PDSCH or EPDCCH. CRS is used for measuring
a propagation path estimation value for performing propagation path compensation for
PDCCH or PDSCH, and/or a channel in the downlink for reporting CSI. CSI-RS is used
for measuring a channel in the downlink for reporting CSI. The channel measurement
unit 2059 calculates RSRP (Reference Signal Received Power) and/or RSRQ (Reference
Signal Received Quality) based on the CRS, CSI-RS, or detection signal, and outputs
the calculated value to the processor 201.
[0087] The transmitter 207 performs transmission processing such as encoding, modulation,
and multiplexing on the uplink control information and uplink data input from the
upper-layer processor 201 under the control of the controller 203. For example, the
transmitter 207 generates and multiplexes uplink channels such as PUSCH or PUCCH and/or
uplink reference signals, and generates transmission signals. The transmission processing
in the transmitter 207 is performed based on predefined settings, or settings or notifications
from the base station device 1. The transmitter 207 includes an encoder 2071, a modulator
2073, a multiplexer 2075, a radio transmitter 2077, and an uplink reference signal
generator 2079.
[0088] The encoder 2071 encodes the HARQ indicator (HARQ-ACK), uplink control information,
and uplink data input from the controller 203 using an encoding method such as block
encoding, convolutional encoding, or turbo encoding. The modulator 2073 modulates
the encoded bits input from the encoder 2071 using a modulation method such as BPSK,
n/2 BPSK, QPSK, 16QAM, 64QAM, or 256QAM. The uplink reference signal generator 2079
generates an uplink reference signal based on the RRC parameters set in the terminal
device 2 and the like.
[0089] The multiplexer 2075 multiplexes modulation symbols and uplink reference signals
for each channel and arranges them in predetermined resource elements.
[0090] The radio transmitter 2077 performs processing on the signal from the multiplexer
2075, such as conversion to a time domain signal by DFT or IFFT, addition of guard
intervals, generation of baseband digital signals, conversion to analog signals, orthogonal
modulation, conversion (upconversion) from an intermediate frequency signal to a high-frequency
signal, removal of extra frequency components, and amplification of power and generates
a transmission signal. The transmission signal output by the radio transmitter 2077
is transmitted from the antenna 209.
[0091] In the configuration described above, the signal waveform transmitted from the base
station device 1 can be switched, but a configuration that can switch the signal waveform
of the signal transmitted from the terminal device 2 may be added. In this case, the
terminal device 2 may be equipped with the same radio transmitter configuration as
the base station device 1 (see Fig. 6), and the base station device 1 may be equipped
with the same radio receiver configuration as the terminal device 2 (see Fig. 10).
<Radio frame structure>
[0092] An example of the radio frame structure of the communication system according to
the present embodiment will be described.
[0093] Fig. 13 shows an example of an NR frame structure as a radio frame structure. A radio
frame has a time interval of 10 ms and includes two half-frames each with a time interval
of 5 ms. Each half-frame includes five subframes. One subframe includes one or more
slots. One slot includes 14 symbols in the case of a normal CP, and 12 symbols in
the case of an extended CP.
<OFDM transmission and DFT-S-OFDM transmission>
[0094] An example of the operation of transmitting a signal from a transmitting device to
a receiving device using OFDM transmission or DFT-S (Spread)-OFDM transmission used
in 5G NR and the like will be explained.
[0095] Fig. 14 shows an example of signal processing on the transmitting side and the receiving
side during 5G NR downlink or uplink transmission. More specifically, Fig. 14 shows
an example of physical layer signal processing performed in each of the transmitting
device and the receiving device when performing downlink or uplink transmission. In
the downlink, the transmitting device is the base station device 1, and the receiving
device is the terminal device 2. In the uplink, the transmitting device is the terminal
device 2 and the receiving device is the base station device 1.
[0096] In the transmitting device, error correction parity bits are added to the transmission
signal sequence by error correction coding (ECC) (S101), and a number bits corresponding
to the number of bits corresponding to the transmission resource and modulation method
are extracted from the encoded bit string by rate matching (S102). Interleaving (S103)
and scrambling (S104) are applied to the bit string including the extracted bits,
and the bit string is mapped to complex signal points by modulation processing (S105).
In the case of transmission in multiple layers (in the case of MIMO transmission),
complex signal points are mapped to each layer (S106). Here, when performing DFT-S-OFDM
transmission (that is, when transmitting a single-carrier signal), transform precoding,
for example, DFT processing is performed (S107). The name transform precoding is just
an example, and other names indicating DFT processing may be used. When performing
OFDM transmission (that is, when transmitting a multi-carrier signal), transform precoding
is omitted. Precoding (that is, setting of transmission weights) for beamforming is
performed (S108), and resource mapping is performed on the precoded signal (S109).
The signal after resource mapping is converted into a time-axis signal by OFDM processing
(IDFT or IFFT, and the like), and the converted signal is transmitted.
[0097] The receiving device converts the received signal into a frequency domain signal
by OFDM processing (DFT or FFT, and the like) (S111), performs resource demapping
on the converted signal, and performs frequency equalization processing to eliminate
distortion due to radio wave propagation (S113). When a signal is transmitted from
a transmitting device using DFT-S-OFDM transmission, transform de-precoding, for example,
IDFT processing, is further performed on the signal after distortion compensation.
If the signal is transmitted from the transmitting device by OFDM transmission, the
IDFT processing is omitted. After that, the signals mapped to multiple layers are
returned (S115), the soft decision value of each bit is obtained from the complex
signal point (S116), and descrambling (S117), deinterleaving (S118), de-rate matching
(S119), and error correction decoding (S120) are executed.
[0098] One of the features of the embodiment of the present disclosure is that the base
station device 1 notifies the terminal device 2 which of the first signal waveform
and the second signal waveform is used in the initial connection procedure, and uses
the notified signal waveform to perform downlink communication. As an example, the
base station device 1 notifies the terminal device 2 in advance of Information (first
information) regarding which signal waveform, the first signal waveform or the second
signal waveform, is used in downlink communication for at least part of the initial
connection procedure performed with the terminal device 2. The first information may
be transmitted in association with a predetermined signal. Various types of predetermined
signals can be considered, such as a synchronization signal, and the details will
be described later. The base station device 1 performs downlink communication (downlink
signal transmission) in the initial connection procedure with the terminal device
2 using a signal waveform based on the notified first information. The terminal device
2 receives the downlink communication signal using the reception processing for the
signal waveform indicated in the first information notified from the base station
device 1. Below, the initial connection procedure will be explained first.
<Initial connection procedure>
[0099] The initial connection procedure will be described below, divided into the following
items.
<Outline of initial connection procedure (initial connection procedure)>
<System information>
<RACH procedure>
<Types of RACH procedures>
<Details of NR PRACH>
<Details of NR random access response>
<Details of NR message 3>
<Details of NR contention resolution>
<NR 2-step RACH procedure>
<Outline of initial connection procedure (initial connection procedure)>
[0100] The initial connection is a procedure performed for the terminal device 2 to transition
from a state in which it is not connected to any cell (idle state) to a state in which
it has established a connection with any cell (connected state).
[0101] Fig. 15 shows an example of an initial connection procedure for the terminal device
2.
[0102] The terminal device 2 in the idle state first performs a cell selection procedure.
The cell selection procedure includes detection of a synchronization signal (S201)
and decoding of a PBCH (Physical Broadcast Channel) (S202). The terminal device 2
performs downlink synchronization with the cell based on the detection of the synchronization
signal. After establishing downlink synchronization, the terminal device attempts
to decode the PBCH and acquires the first system information (S203). Furthermore,
the terminal device 2 acquires second system information based on the first system
information included in the PBCH (S203). Next, the terminal device 2 performs a random
access procedure (random access procedure, RACH (Random Access Channel) procedure,
RACH procedure) based on the first system information and/or the second system information.
The random access procedure includes sending a random access preamble, receiving a
random access response, sending message 3, and receiving a contention resolution.
More details are as follows.
[0103] The terminal device 2 first selects a predetermined PRACH (Physical Random Access
Channel) preamble and transmits the selected preamble (random access preamble) (S204).
The random access preamble is transmitted in association with PRACH. The random access
preamble is also referred to as message 1.
[0104] Next, a PDSCH (Physical Downlink Shared Channel) including a random access response
corresponding to the PRACH preamble is received (S205). That is, the random access
response is transmitted on the PDSCH. A PDSCH including a random access response is
scheduled on a PDCCH (Physical Downlink Control Channel). The random access response
is also referred to as message 2.
[0105] Next, the PUSCH including message 3 is transmitted using the resources scheduled
by the random access response grant included in the random access response (S206).
The PUSCH including message 3 is scheduled by the uplink grant included in the random
access response. Message 3 includes an RRC (Radio Resource Control) message requesting
an RRC connection.
[0106] Finally, the PDSCH including contention resolution corresponding to the PUSCH is
received (S207). Contention resolution includes RRC messages for RRC connection setup.
The contention resolution includes, for example, information regarding which terminal
device the base station device 1 has connected to. Contention resolution is also referred
to as message 4. The RRC connection setup complete message is also referred to as
message 5.
[0107] When the terminal device 2 receives the RRC message for RRC connection setup, the
terminal device 2 performs an RRC connection operation and transitions from the RRC
idle state to the RRC connected state. After transitioning to the RRC connected state,
the terminal device 2 transmits an RRC message indicating the completion of RRC connection
setup to the base station device 1. Through this series of operations, the terminal
device 2 can connect to the base station device 1. That is, after all steps of the
random access procedure are completed, the terminal device 2 can transition to a state
where it is connected to the cell (connected state).
[0108] The random access procedure in Fig. 15 is also referred to as a 4-step RACH procedure.
On the other hand, the random access procedure in which the terminal device 2 sends
the message 3 along with the transmission of the random access preamble (message 1),
and the base station device 1 sends a random access response (message 2) and a contention
resolution (message 4) as a response is referred to as a 2-step RACH procedure. As
an initial connection procedure for the terminal device 2, it is also possible to
perform a 2-step RACH procedure (see Fig. 18 described later).
<System information>
[0109] The system information transmitted from a cell is information that broadcasts settings
in the cell. The system information includes, for example, information regarding access
to the cell, information regarding cell selection, information regarding other RATs
(Radio Access Technology) and other systems, and the like.
[0110] System information can be classified into MIB (Master Information Block) and SIB
(System Information Block). MIB is information on a fixed payload size that is broadcast
via PBCH. The MIB includes information for acquiring the SIB. SIB is system information
other than MIB. SIB is broadcast by PDSCH.
[0111] In addition, the system information can be classified into first system information,
second system information, and other system information (third system information
and the like). The first system information and the second system information include
information regarding access to the cell for transmitting these pieces of system information,
information regarding acquisition of other system information (third system information),
and information regarding cell selection. The information included in the MIB can
be considered as first system information, and the information included in SIB 1 can
be considered as second system information. If the terminal device cannot acquire
the first system information from the cell, it is assumed that access to the cell
is prohibited.
[0112] The MIB is physical layer information necessary to receive system information such
as second system information. The MIB includes a part of the system frame number,
subcarrier spacing information (at least message 2/4 for SIB1 and initial connection
and paging and broadcast SI message subcarrier spacing information), subcarrier offset
information, DMRS type A position information, PDCCH settings for at least SIB1, cell
barred information, and intra-frequency reselection information.
[0113] SIB1 includes information regarding cell selection, information regarding cell access,
information regarding connection establishment failure control, scheduling information
of system information other than SIB1, serving cell settings, and the like. The serving
cell configuration includes cell-specific parameters, such as downlink configuration,
uplink configuration, TDD configuration information, and the like. Uplink settings
include RACH settings and the like.
<RACH procedure>
[0114] The random access procedure (RACH procedure) is performed to achieve the following
objectives, for example.
- RRC connection setup from idle state to inactive or connected state
- Request for state transition from inactive state to connected state
- Handover to switch connected cells
- Scheduling request to request resources for uplink data transmission
- Timing advance adjustment to adjust uplink synchronization
- On-demand SI requests requesting system information that has not been sent
- Recovery of interrupted beam connection (beam recovery)
[0115] RRC connection setup from an idle state to an inactive state or a connected state
is an operation performed when a terminal device connects to a base station device
in response to the occurrence of traffic. Specifically, this operation is an operation
in which connection information (for example, UE context) is passed from the base
station device to the terminal device. The UE context is managed using predetermined
terminal device identification information (for example, C-RNTI) instructed by the
base station device. When the terminal device completes this operation, the terminal
device transitions from an idle state to an inactive state or from an idle state to
a connected state.
[0116] The request for a state transition from an inactive state to a connected state is
a request for a state transition from an inactive state to a connected state in response
to the occurrence of traffic. By transitioning to the connected state, the terminal
device can transmit and receive unicast data to and from the base station device.
[0117] Handover, which switches the connected cell, is an operation that switches the connection
from a connected cell (serving) to a cell adjacent to the cell (neighbor cell) due
to changes in the radio wave environment such as movement of the terminal device.
The terminal device that receives the handover command from the base station device
makes a connection request to the neighbor cell specified by the handover command.
[0118] The scheduling request is an operation for requesting resources for uplink data transmission
depending on the occurrence of traffic. After successfully receiving this scheduling
request, the base station device allocates PUSCH resources to the terminal device.
Note that the scheduling request is also made by PUCCH.
[0119] Timing advance adjustment for adjusting uplink synchronization is an operation for
adjusting frame errors between downlink and uplink caused by propagation delay. The
terminal device transmits the PRACH at a timing adjusted with respect to the downlink
frame. Accordingly, the base station device can recognize the propagation delay with
the terminal device, and can instruct the terminal device about the timing advance
value using message 2 or the like. The timing advance value is an example of information
regarding the transmission timing of the terminal device in the uplink.
[0120] An on-demand SI request that requests system information that has not been transmitted
is a request for a terminal device to transmit system information to a base station
device when the terminal device needs system information that has not been transmitted
due to system information being overhead, for example.
[0121] Recovery of interrupted beam connection (beam recovery) is an operation that requests
the recovery of a beam when the communication quality deteriorates due to movement
of the terminal device or interruption of the communication path by another object
after the beam has been established. The base station device that receives this request
tries to connect to the terminal device using a different beam.
<Types of RACH procedures>
[0122] Random access procedures (RACH procedures) include contention-based RACH procedures
and non-contention-based RACH procedures.
[0123] Fig. 16 shows an example of a contention-based RACH procedure. The contention-based
RACH procedure is a RACH procedure performed under the initiative of the terminal
device. The contention-based RACH procedure is a 4-step procedure starting with sending
message 1 from the terminal device. The terminal device selects a RACH resource and
a PRACH preamble from a plurality of preset RACH resources and a plurality of PRACH
preambles, and transmits the selected RPA preamble (that is, transmits the PRACH)
using the selected RACH resource. The subsequent steps for transmitting and receiving
messages 2 to 4 are similar to those described in Fig. 15 above. Since these multiple
RACH resources and multiple PRACH preambles are shared with other terminal devices,
PRACHs transmitted from the terminal device may collide.
[0124] Fig. 17 shows an example of a non-contention-based RACH procedure. The non-contention-based
RACH procedure is a RACH procedure performed under the initiative of the base station
device. The non-contention-based RACH procedure can be used, for example, when causing
a terminal device to perform handover. The non-contention-based RACH procedure is
a 3-step procedure starting with the transmission of a PDCCH order from the base station
device. A PDCCH order is transmitted from the base station device, and the terminal
device transmits PRACH using the PRACH preamble specified in the PDCCH order. The
base station device that receives the PRACH transmits a random access response (RA
response) to the terminal device. Since the base station device schedules the PRACH
preamble, the possibility of PRACH contention occurring is low.
<Details of NR-PRACH>
[0125] PRACH in NR (NR-PRACH) is configured using the Zadoff-Chu sequence. In NR-PRACH,
multiple preamble formats are defined. The preamble format is defined by a combination
of parameters such as PRACH subcarrier spacing, transmission bandwidth, sequence length,
number of symbols used for transmission, number of transmission repetitions, CP length,
and guard period length.
[0126] For a terminal device in an idle mode, settings regarding NR-PRACH are made using
system information. Furthermore, settings regarding the NR-PRACH are made for the
terminal device in the connected mode by dedicated RRC signaling.
[0127] NR-PRACH is transmitted using physical resources (frequency and time resources referred
to as NR-PRACH occasions) that can transmit NR-PRACH. The physical resources are indicated
by the configuration for NR-PRACH. The terminal device selects one of the physical
resources and transmits the NR-PRACH. Furthermore, the terminal device in a connected
mode transmits NR-PRACH using NR-PRACH resources. The NR-PRACH resource is a combination
of the NR-PRACH preamble and the physical resources of the preamble. The base station
device can instruct the terminal device to use the NR-PRACH resource.
[0128] Numbers are assigned to the types of NR-PRACH preamble sequences. The NR-PRACH preamble
sequence type number is referred to as a preamble index.
[0129] NR-PRACH is retransmitted when the random access procedure fails. When retransmitting
the NR-PRACH, the terminal device waits for transmission of the NR-PRACH for a waiting
period calculated from the backoff value (backoff indicator: BI). The backoff value
may differ depending on the terminal device category of the terminal device and/or
the priority of the generated traffic. A plurality of backoff values are notified
to the terminal device, and the terminal device selects the backoff value to be used
depending on the priority. Furthermore, when retransmitting the NR-PRACH, the terminal
device increases the transmission power of the NR-PRACH compared to the transmission
power at the time of initial transmission. This operation is referred to as power
ramping.
<Details of NR random access response>
[0130] The NR random access response is sent on the NR-PDSCH.
[0131] NR-PDSCH containing random access response is scheduled by NR-PDCCH. The CRC of the
NR-PDCCH is scrambled by the RA-RNTI. NR-PDCCH is transmitted on the common control
subband. NR-PDCCH is arranged in CSS (Common Search Space). Note that the value of
RA-RNTI is determined based on the transmission resources (time resources (slots or
subframes) and frequency resources (resource blocks)) of the NR-PRACH corresponding
to the random access response. Note that the NR-PDCCH may be arranged in a search
space associated with the NR-PRACH associated with the random access response. Specifically,
the search space in which the NR-PDCCH is arranged is set in association with the
preamble of the NR-PRACH and/or the physical resource on which the NR-PRACH is transmitted.
The search space in which the NR-PDCCH is allocated is set in association with its
preamble index and/or its physical resource index.
[0132] The NR-PDCCH is QCL (Quasi Co-Location) with respect to NR-SS (Synchronization Signal).
[0133] The NR random access response is MAC information. The NR random access response includes
at least an uplink grant for transmitting the NR message 3, a timing advance value
used to adjust uplink frame synchronization, and a temporary C-RNTI value. In addition,
the NR random access response includes the PRACH index used in the NR-PRACH transmission
corresponding to the random access response. The NR random access response also includes
information regarding backoff used for waiting for PRACH transmission. The base station
device transmits an NR random access response including this information on the NR-PDSCH.
[0134] The terminal device determines whether the transmission of the random access preamble
is successful or not from the information included in the NR random access response.
If the terminal device determines that the transmission of the random access preamble
has been successful, the terminal device performs the processing of transmitting the
NR message 3 according to the information included in the random access response.
On the other hand, if the terminal device determines that the random access preamble
transmission has failed, the terminal device considers that the random access procedure
has failed and performs the NR-PRACH retransmission processing.
[0135] Note that the NR random access response may include a plurality of uplink grants
for transmitting the NR message 3. The terminal device can select one resource to
transmit message 3 from a plurality of uplink grants. Accordingly, when a plurality
of terminal devices receives the same random access response, it is possible to reduce
or alleviate the possibility that messages 3 transmitted from the plurality of terminal
devices will collide at the base station device. Accordingly, a more stable random
access procedure can be provided.
<Details of NR message 3>
[0136] NR message 3 is sent on the NR-PUSCH. NR-PUSCH is transmitted using the resources
indicated by the random access response.
[0137] NR message 3 includes an RRC connection request message.
[0138] The waveform or transmission method of the NR-PUSCH transmitted including the NR
message 3 is specified by parameters included in the system information. Specifically,
OFDM (multi-carrier signal) or DFT-s-OFDM (single-carrier signal) is determined according
to parameter instructions.
[0139] When the base station device normally receives the NR message 3, it proceeds to transmission
processing for contention resolution. On the other hand, if the base station device
cannot normally receive the NR message 3, the base station device can try to receive
the NR message 3 again for at least a predetermined period.
[0140] An example of an instruction in the case of instructing retransmission of message
3 and instructing transmission resources is an instruction using NR-PDCCH. The NR-PDCCH
includes an uplink grant. The DCI of the NR-PDCCH indicates the resource for retransmitting
message 3. The terminal device retransmits message 3 based on the uplink grant instructions.
[0141] Note that, if the terminal device does not successfully receive the NR contention
resolution within a predetermined period, the terminal device considers that the random
access procedure has failed, and performs the NR-PRACH retransmission processing.
[0142] Note that the transmission beam of the terminal device used to retransmit the NR
message 3 may be different from the transmission beam of the terminal device used
to transmit the message 3 for the first time.
[0143] Note that, if the terminal device fails to receive either the NR contention resolution
or the message 3 retransmission instruction within a predetermined period, the terminal
device considers that the random access procedure has failed and performs the NR-PRACH
retransmission processing. The predetermined period is set, for example, by system
information.
<Details of NR contention resolution>
[0144] NR contention resolution is sent on the NR-PDSCH.
[0145] NR-PDSCH including contention resolution is scheduled by NR-PDCCH. The CRC of the
NR-PDCCH is scrambled by the temporary C-RNTI or C-RNTI. NR-PDCCH is arranged in USS
(terminal device-specific search space). Note that the NR-PDCCH may be placed in the
CSS.
[0146] When the terminal device successfully receives the NR-PDSCH including contention
resolution, the terminal device responds with an ACK to the base station device. Thereafter,
the terminal device assumes that this random access procedure has been successful
and enters a connected state. On the other hand, if the base station device receives
a NACK for the NR-PDSCH including contention resolution from the terminal device,
or if there is no response from the terminal device, the base station device retransmits
the NR-PDSCH including contention resolution. Furthermore, if the terminal device
cannot receive the NR contention resolution within a predetermined period, the terminal
device considers that the random access procedure has failed and performs the NR-PRACH
retransmission processing.
<NR 2-step RACH procedure>
[0147] Fig. 18 is a sequence diagram showing an example of the NR 2-step RACH procedure.
The 2-step RACH procedure consists of two steps: transmission of message A (Message.A)
from the terminal device and transmission of message B (Message.B) from the base station
device. As an example, message A includes message 1 (Preamble) and message 3 in the
conventional 4-step RACH, and message B includes message 2 and message 4 in the conventional
4-step RACH. Furthermore, as an example, message A is configured with PRACH (Preamble)
and PUSCH, and message B is configured with PDSCH.
[0148] By adopting a 2-step random access procedure, it becomes possible to complete the
random access procedure with lower latency than the conventional 4-step random access
procedure.
[0149] Regarding the Preamble and PUSCH (message 3) included in Message.A, respective transmission
resources may be set in association with each other, or respective independent resources
may be set.
[0150] When transmission resources are set in association, for example, when a Preamble
transmission resource is determined, a PUSCH transmission resource that can be a unique
candidate or a plurality of candidates is determined. As an example, the time offset
and frequency offset between the Preamble of the PRACH occasion and the PUSCH occasion
are determined by one value. As another example, the time offset and frequency offset
between the Preamble of the PRACH occasion and the PUSCH occasion are determined to
have different values for each preamble. The offset value may be determined according
to specifications, or may be set quasi-statically by the base station device. As an
example of the values of the time offset and the frequency offset, they are defined
depending on the frequency to be used, for example. For example, in an unlicensed
band (5 GHz band, band 45), the time offset value can be set to 0 or a value close
to 0. In this way, it is possible to omit LBT (Listen Before Talk) before transmitting
the PUSCH.
[0151] On the other hand, when independent resources are configured, the transmission resources
for Preamble and PUSCH may be determined based on the specifications. Alternatively,
each transmission resource may be semi-statically set by the base station device,
or each transmission resource may be determined from other information. Other information
includes, for example, Slot format information (Slot Format Indicator, etc.), Band
Width Part (BWP) information, Preamble transmission resource information, Slot Index,
and Resource Block Index. In addition, if independent resources are set, the association
between the Preamble constituting one Message.A and the PUSCH (message 3) may be notified
to the base station by the payload of the PUSCH or the UCI included in the PUSCH.
Alternatively, the association may be notified to the base station by the transmission
physical parameters of the PUSCH. The transmission physical parameters include, for
example, a PUSCH scrambling sequence, a DMRS sequence and/or pattern, and a PUSCH
transmission antenna port.
[0152] In addition, regarding the setting method of transmission resources for Preamble
and PUSCH, it may be possible to switch between a case where they are set in association
with each other and a case where they are set as independent resources. For example,
in a licensed band, a case where independent resources are set may be applied, and
in an unlicensed band, a case where transmission resources are set in association
may be applied.
<Communication processing flow>
[0153] Fig. 19 is a sequence diagram illustrating an example of the flow of communication
processing in the radio communication system according to the embodiment of the present
disclosure. This communication processing includes an initial connection procedure
(S301 to S306) of the terminal device 2 performed with the base station device 1,
and arbitrary processing in the subsequent time segment (S307, S308).
[0154] A synchronization signal is transmitted from the base station device 1 with a predetermined
signal waveform (S301), and the terminal device 2 receives (detects) this synchronization
signal (S301). After establishing downlink synchronization, the terminal device 2
attempts to decode a PBCH (Physical Broadcast Channel) and acquires the first system
information. Furthermore, the terminal device 2 acquires second system information
(for example, SIB) based on the first system information included in the PBCH. SIB
is broadcast by PDSCH.
[0155] The terminal device 2 determines the signal waveform to be used by the base station
device 1 in subsequent downlink communications in the initial connection procedure
(S303). The signal waveform is, for example, either a second signal waveform including
a single-carrier signal or a first signal waveform including a multi-carrier signal.
Information regarding the signal waveform to be used (first information or signal
waveform identification information) is associated with a predetermined signal transmitted
from the base station device 1, and is acquired in advance by the terminal device
2 at an arbitrary timing (for example, from step S101 to step S303). That is, the
base station device 1 determines which of the first signal waveform and the second
signal waveform to be used in downlink communication in the initial connection procedure,
and transmits information (first information or signal waveform identification information)
regarding the determined signal waveform to the terminal device 2 in association with
a predetermined signal. Examples of the predetermined signal include the above-mentioned
synchronization signal, PBCH, or PDSCH. Details of the predetermined signal and signal
waveform identification information will be described later.
[0156] The terminal device 2 performs a random access procedure (RACH procedure) based on
the first system information and/or the second system information. The random access
procedure is basically the same as steps S204 to S207 in Fig. 15. However, in the
processing flow of Fig. 19, the base station device 1 controls the radio transmitter
1077 (see Fig. 10) to perform transmission processing using the signal waveform notified
to the terminal device 2 in advance. The terminal device 2 controls the radio receiver
2057 (see Fig. 15) to perform reception processing for the signal waveform determined
in step S303.
[0157] Specifically, the terminal device 2 first selects a predetermined PRACH (Physical
Random Access Channel) preamble and transmits the selected preamble (random access
preamble) (S304). The random access preamble is transmitted in association with PRACH.
The random access preamble is also referred to as message 1.
[0158] As downlink communication, the base station device 1 transmits a PDSCH (Physical
Downlink Shared Channel) including a random access response corresponding to the PRACH
preamble using a signal waveform notified to the terminal device 2 in advance (S305).
Specifically, when transmitting the second signal waveform (single-carrier signal),
the base station device 1 sets the output destination of the signal waveform switch
401 to the second signal waveform transmitter 405. When transmitting the first signal
waveform (multi-carrier signal), the base station device 1 sets the output destination
of the signal waveform switch 401 to the first signal waveform transmitter 403.
[0159] The terminal device 2 receives the PDSCH including the random access response using
the reception processing for the signal waveform determined in step S303 (step S305).
That is, when receiving a single-carrier signal, the terminal device 2 sets the output
destination of the signal waveform switch 301 to the second signal waveform receiver
305. When receiving a multi-carrier signal, the terminal device 2 sets the output
destination of the signal waveform switch 301 to the first signal waveform receiver
303. Note that the PDSCH including the random access response is scheduled on the
PDCCH (Physical Downlink Control Channel). The random access response is also referred
to as message 2.
[0160] The terminal device 2 transmits the PUSCH including the message 3 using the resources
scheduled by the random access response grant included in the random access response
(S306). The PUSCH including message 3 is scheduled by the uplink grant included in
the random access response. Message 3 includes an RRC (Radio Resource Control) message
requesting an RRC connection.
[0161] In downlink communication, the base station device 1 transmits a PDSCH including
contention resolution corresponding to the PUSCH using the above-mentioned signal
waveform (S307). Specifically, when transmitting a single-carrier signal, the base
station device 1 sets the output destination of the signal waveform switch 401 to
the second signal waveform transmitter 405. When transmitting a multi-carrier signal,
the base station device 1 sets the output destination of the signal waveform switch
401 to the first signal waveform transmitter 403.
[0162] The terminal device 2 receives the PDSCH including contention resolution using the
reception processing for the signal waveform determined in step S303 (step S307).
That is, when receiving a single-carrier signal, the output destination of the signal
waveform switch 301 is set to the second signal waveform receiver 305. When receiving
a multi-carrier signal, the output destination of the signal waveform switch 301 is
set to the first signal waveform receiver 303. Contention resolution includes RRC
messages for RRC connection setup. The contention resolution includes, for example,
information regarding which terminal device is connected. Contention resolution is
also referred to as message 4. The RRC connection setup complete message is also referred
to as message 5.
[0163] When the terminal device 2 receives the RRC message for RRC connection setup, the
terminal device 2 performs an RRC connection operation and transitions from the RRC
idle state to the RRC connected state. After transitioning to the RRC connected state,
the terminal device 2 transmits an RRC message indicating the completion of RRC connection
setup to the base station device 1. Through this series of operations, the terminal
device 2 can connect to the base station device 1. That is, after all steps of the
random access procedure are completed, the terminal device 2 can transition to a state
where it is connected to the cell (connected state).
[0164] The base station device 1 re-determines the signal waveform to be used in downlink
communication in an arbitrary time segment after completion of the initial connection,
and transmits information (first information or signal waveform identification information)
regarding the determined signal waveform to the terminal device 2 in association with
a predetermined signal (S308). In the illustrated example sequence, the predetermined
signal is RRC signaling (RRC message or RRC parameter). The signal waveform of RRC
signaling may be a predetermined signal waveform, or the same signal waveform as before
may be used continuously as long as there is no change in the signal waveform to be
used. In the latter case, the base station device 1 performs RRC signaling using the
same signal waveform as the signal waveform to be used in the previous downlink communication.
[0165] Thereafter, the base station device 1 may repeatedly perform processes similar to
steps S308 and S309 at an arbitrary timing or periodically to switch the signal waveform
to be used.
[0166] Note that the signal waveform identification information may be in the form of explicit
information or implicit information. For example, if the frequency (channel) of a
signal received from the base station device 1 itself also serves as signal waveform
identification information, the signal waveform identification information can be
said to be implicit information. Details of the signal waveform identification information
will be described later.
[0167] In the operation example of Fig. 19, the base station device 1 transmits signal waveform
identification information (first information) to the terminal device 2, and transmits
a signal with the signal waveform indicated by the signal waveform identification
information after transmitting the signal waveform identification information. That
is, the signal transmitted using the signal waveform is a signal different from the
predetermined signal for which the signal waveform identification information is notified.
As another example, the signal waveform identification information may be included
in the signal itself transmitted using the signal waveform. In this case, the signal
waveform identification information is detected in the signal waveform switch 301
in the radio receiver 2057 of the terminal device 2 or in the processing at the preceding
stage thereof.
[0168] Although Fig. 19 shows an example in which a 4-step RACH procedure is performed as
an initial connection procedure, a similar operation is possible when a 2-step RACH
procedure is performed. That is, the base station device 1 determines a signal waveform
to be used in downlink communication in an initial procedure, and transmits information
(first information or signal waveform identification information) regarding the determined
signal waveform to the terminal device 2. The terminal device 2 determines the signal
waveform to be transmitted from the base station device 1 in the initial procedure
based on the information. In the subsequent procedure in the 2-step RACH, the terminal
device 2 receives the downlink signal transmitted from the base station device 1 using
the reception processing for the signal waveform determined by the determination.
[0169] In the initial connection procedure of Fig. 19, after the transmission/reception
of the synchronization signal, at least one of the following is included, for example.
- PBCH transmission/reception
- PDSCH transmission/reception
- PDCCH transmission/reception
- 4-step RACH procedure or 2-step RACH procedure
<Single-carrier signal and multi-carrier signal>
[0170] Single-carrier signals and multi-carrier signals will be explained in detail. The
single-carrier signal or the second signal waveform is a signal that has been subjected
to transform precoding, and the multi-carrier signal or the first signal waveform
is a signal that has not been subjected to transform precoding. More specifically,
a single-carrier signal is a signal that has been subjected to transform precoding
before OFDM processing (here, IDFT or IFFT) on the transmitting side. A multi-carrier
signal is a signal that has not been subjected to transform precoding before OFDM
processing (here, IDFT or IFFT) on the transmitting side. As an example, the transform
precoding is DFT or FFT. In other words, a single-carrier signal is a signal that
is subjected to IDFT or FFT after OFDM processing (here, DFT or FFT) on the receiving
side. A multi-carrier signal is a signal that is not subjected to IDFT or FFT after
OFDM processing (here, DFT or FFT) on the receiving side.
[0171] Examples of single-carrier signals include a DFT-S-OFDM signal (SC-FDMA signal),
an SC-QAM signal, a single-carrier with zero padding/unique word, and the like. Examples
of multi-carrier signals include OFDM signals or CP-OFDM signals.
[0172] In the present embodiment, during the initial connection procedure and other time
segments, it is possible to selectively switch between a single-carrier signal and
a multi-carrier signal as a signal waveform to be used in downlink communication.
However, the types of signal waveforms used in downlink communication are not limited
to single-carrier signals and multi-carrier signals. Generally, as a signal waveform
to be used in downlink communication, at least a first signal waveform and a second
signal waveform can be selectively switched. It may also be possible to selectively
switch between three or more signal waveforms.
[0173] As an example, the first signal waveform is a multi-carrier signal and the second
signal waveform is a single-carrier signal. The first signal waveform is not limited
to a multi-carrier signal, and may be a signal waveform different from the multi-carrier
signal. For example, the first signal waveform may be a signal waveform using a method
other than OFDM as secondary modulation, such as, for example, CDMA (Code Division
Multiple Access) signals, DS (Direct Sequence or Direct Spread) signals, DS-CDMA (Direct
Spread-Code Division Multiple Access), or FF signals (Frequency Hopping). In addition,
the first signal waveform may be a signal waveform in which primary modulation is
performed and secondary modulation is not performed, for example.
<Example of predetermined signal>
[0174] An example of a predetermined signal regarding signal waveform identification information
(first information) is shown below. The predetermined signal is not limited to the
signals shown below.
- PSS (Primary Synchronization Signal), SSS (Secondary Synchronization signal), TSS
(Tertiary Synchronizations) signal) or other synchronization signal
- PBCH (Physical Broadcast channel)
- PDSCH (Physical Downlink Shared Channel), for example, PDSCH including SI (System
Information)
- RS (Reference Signal) For example, DMRS transmitted in conjunction with at least one
of PBCH and PDSCH
- Newly defined signal that notifies the terminal device of the signal waveform to be
used in the downlink
<Example of signal waveform identification information and operation example of base
station device 1 and terminal device 2 regarding signal waveform identification information>
[0175] Examples of signal waveform identification information are shown below. In addition,
for each example of signal waveform identification information, an operation example
in which the base station device 1 transmits the signal waveform identification information,
and an operation example in which the terminal device 2 determines the signal waveform
based on the signal waveform identification information and switches reception processing
is shown. Note that the signal waveform identification information is not limited
to the information shown below as long as it is information that allows the terminal
device 2 to identify or recognize the signal waveform.
[1]Information regarding generation of sequence of PSS, SSS, TSS or other synchronization
signals
[0176] The base station device 1 includes a determination term representing either the first
signal waveform or the second signal waveform in the generation formula for the sequence
of PSS, SSS, TSS, or other synchronization signals. The determination term may be
expressed by, for example, 1 bit.
[0177] For example, when using the first signal waveform for downlink communication in the
initial connection procedure, the base station device 1 includes the determination
term representing the first signal waveform in the generation formula for the sequence
of any of the synchronization signals described above. After transmitting any of the
synchronization signals described above, the base station device 1 transmits a signal
with the first signal waveform in downlink communication in the initial connection
procedure. When the base station device 1 uses the second signal waveform for downlink
communication in the initial connection procedure, the base station device 1 includes
a determination term representing the second signal waveform in the generation formula
for the sequence of any of the synchronization signals described above. After transmitting
any of the synchronization signals described above, the base station device 1 transmits
a signal with the second signal waveform in downlink communication in the initial
connection procedure.
[0178] The terminal device 2 on the receiving side detects the determination term included
in the information received from the base station device 1 (the generation formula
for the sequence of any of the synchronization signals described above), thereby determining
which of the first signal waveform or the second signal waveform will be used in downlink
communication during the initial connection procedure. If the determination term indicates
the first signal waveform, the terminal device 2 switches the output destination of
the signal waveform switch 301 to the first signal waveform receiver 303. Accordingly,
the terminal device 2 sets reception processing for the first signal waveform. If
the determination term indicates the second signal waveform, the output destination
of the signal waveform switch 301 is switched to the second signal waveform receiver
305. Accordingly, the terminal device 2 sets reception processing for the second signal
waveform. Thereafter, the terminal device 2 receives the signal transmitted by downlink
communication from the base station device 1 using the set reception processing (reception
processing for the first signal waveform or the second signal waveform).
[0179] After the initial connection procedure is completed, the base station device 1 may
continue to use the same signal waveform. If the signal waveform is set during the
initial connection procedure, the base station device 1 may use the set signal waveform.
If a default signal waveform exists, the default signal waveform may be restored.
[0180] Although an example of switching (or controlling) the signal waveform to be used
in the initial connection procedure has been described here, similar processing is
also possible when switching the signal waveform to be used in an arbitrary time segment
after the initial connection procedure.
[2]Information regarding frequency resource on which predetermined signal is transmitted
[0181] Information regarding frequency resources is information that specifies frequency
resources, such as subcarriers, resource blocks, component carriers, and BWPs (Band
Width Parts). In addition, the information regarding the frequency resource may be
information regarding the size of the frequency resource, such as the number of subcarriers
or the number of resource blocks.
[0182] The base station device 1 controls (switches) the signal waveform to be used in the
initial connection procedure according to the frequency resource for transmitting
a predetermined signal. Hereinafter, an example in which the frequency resources are
resource blocks will be explained, but any information regarding the frequency resources
is applicable without being limited to resource blocks. For example, when transmitting
a predetermined signal using a specific resource block, the base station device 1
performs downlink communication in the initial connection procedure using the first
signal waveform. That is, after transmitting a predetermined signal, the base station
device 1 transmits a signal with the first signal waveform in downlink communication
in the initial connection procedure. When transmitting a predetermined signal using
a resource block different from a specific resource block, the base station device
1 performs downlink communication in the initial connection procedure using the second
signal waveform. That is, after transmitting a predetermined signal, the base station
device 1 transmits a signal with the second signal waveform in downlink communication
in the initial connection procedure. Note that the predetermined signal itself is
transmitted with an arbitrary signal waveform or a predetermined signal waveform.
In the description of this paragraph, the first signal waveform and the second signal
waveform may be reversed.
[0183] The terminal device 2 controls reception processing used for downlink reception in
the initial connection procedure, depending on the resource block that receives a
predetermined signal. For example, if the resource block that received the predetermined
signal is a specific resource block, the terminal device 2 uses the reception processing
for the second signal waveform to receive downlink communication in the initial connection
procedure. If the resource block to which the predetermined signal is transmitted
is not a specific resource block, the downlink communication in the initial connection
procedure is received using the reception processing for the first signal waveform.
Note that the resource block is specified by a resource block index. In the description
of this paragraph, the first signal waveform and the second signal waveform may be
reversed.
[0184] Information regarding the frequency resource on which a predetermined signal is transmitted
may be notified from the base station device 1 to the terminal device 2 before transmitting
the predetermined signal or in a state of being included in the predetermined signal,
or such notification may be unnecessary. In this case, the terminal device 2 may detect
the frequency resource on which the predetermined signal is received. In this case,
the base station device 1 does not need to explicitly transmit information regarding
the frequency resource on which the predetermined signal is transmitted.
[0185] Furthermore, the base station device 1 controls the signal waveform to be used in
the initial connection procedure according to the number of resource blocks transmitting
a predetermined signal. For example, when the number of resource blocks that transmit
a predetermined signal is a predetermined number, the base station device 1 performs
downlink communication in the initial connection procedure using the first signal
waveform. That is, after transmitting a predetermined signal, the base station device
1 transmits a signal with the first signal waveform in downlink communication in the
initial connection procedure. If the number of resource blocks that transmit the predetermined
signal is not the predetermined number, the base station device 1 performs downlink
communication in the initial connection procedure using the second signal waveform.
That is, after transmitting a predetermined signal, the base station device 1 transmits
a signal with the second signal waveform in downlink communication in the initial
connection procedure. The predetermined signal itself is transmitted with an arbitrary
signal waveform or a predetermined signal waveform. In the description of this paragraph,
the first signal waveform and the second signal waveform may be reversed.
[0186] The terminal device 2 controls reception processing used in downlink communication
in the initial connection procedure according to the number of resource blocks in
which a predetermined signal has been received. For example, when the number of resource
blocks in which a predetermined signal has been received is a predetermined value,
the terminal device 2 uses the reception processing for the first signal waveform
to receive downlink communication in the initial connection procedure. If the number
of symbols in which the predetermined signal is received is not the predetermined
number, reception processing for the second signal waveform is used to receive downlink
communication in the initial connection procedure. In the description of this paragraph,
the first signal waveform and the second signal waveform may be reversed.
[0187] Information regarding the number of resource blocks to which a predetermined signal
is transmitted may be notified from the base station device 1 to the terminal device
2 before transmitting the predetermined signal or in a state of being included in
the predetermined signal, or such notification may be unnecessary. In this case, the
terminal device 2 may detect the number of resource blocks in which a predetermined
signal has been received from the received predetermined signal. In this case, the
base station device 1 does not need to explicitly transmit information regarding the
resource block to which the predetermined signal is transmitted.
[0188] In the initial connection procedure or an arbitrary time segment thereafter, the
base station device 1 may control the signal waveform to be used according to the
resource block or the number of resource blocks to be used each time downlink communication
is performed. The terminal device 2 may control reception processing applied to the
signal received from the base station device 1 according to the resource block or
the number of resource blocks of the received signal. Accordingly, the base station
device 1 and the terminal device 2 can selectively switch the signal waveform to be
used and reception processing each time downlink communication is performed.
[3]Information regarding time resources in which predetermined signal is transmitted
[0189] Information regarding time resources information that specifies time resources, such
as, for example, symbols, mini-slots (non-slot-based), slots, subframes, frames, or
radio frames. In addition, the information regarding the time resource may be information
regarding the size of the time resource, such as the number of symbols or the number
of slots.
[0190] The base station device 1 controls the signal waveform to be used in the initial
connection procedure according to the time resource for transmitting a predetermined
signal. For example, when transmitting a predetermined signal using a specific time
resource (for example, a symbol), the base station device 1 performs downlink communication
in the initial connection procedure using the first signal waveform. In other words,
when using the first signal waveform in downlink communication in the initial connection
procedure, the base station device 1 transmits a predetermined signal with a specific
time resource. After transmitting the predetermined signal, the base station device
1 transmits a signal with a second signal waveform in downlink communication in the
initial connection procedure. In the description of this paragraph, the first signal
waveform and the second signal waveform may be reversed.
[0191] When transmitting a predetermined signal using a time resource other than a specific
time resource (for example, a symbol), the base station device 1 performs downlink
communication in the initial connection procedure using the second signal waveform.
In other words, when using the second signal waveform in downlink communication in
the initial connection procedure, the base station device 1 transmits the predetermined
signal using a time resource other than the specific time resource. After transmitting
the predetermined signal, the base station device 1 transmits a signal with a second
signal waveform in downlink communication in the initial connection procedure. The
predetermined signal itself is transmitted with an arbitrary signal waveform or a
predetermined signal waveform. In the description of this paragraph, the first signal
waveform and the second signal waveform may be reversed.
[0192] The terminal device 2 controls reception processing used in downlink communication
in the initial connection procedure, according to the time resource (for example,
symbol) in which the predetermined signal is received. For example, if the time resource
in which the predetermined signal is received is a specific time resource, the terminal
device 2 uses the reception processing for the first signal waveform to receive downlink
communication in the initial connection procedure. If the time resource in which the
predetermined signal is received is not a specific time resource, the terminal device
2 receives the downlink communication in the initial connection procedure using the
reception processing for the second signal waveform. Note that the symbol is specified
by a symbol index. In the description of this paragraph, the first signal waveform
and the second signal waveform may be reversed.
[0193] Information regarding the time resources in which a predetermined signal is received
may be notified from the base station device 1 to the terminal device 2 before transmitting
the predetermined signal or in a state of being included in the predetermined signal,
or such notification may be unnecessary. In this case, the terminal device 2 may detect
the time resource in which the predetermined signal was received from the received
predetermined signal. In this case, the base station device 1 does not need to explicitly
transmit information regarding the time resources for transmitting the predetermined
signal.
[0194] As another example, the base station device 1 controls the signal waveform to be
used in the initial connection procedure according to the number of time resources
(for example, the number of symbols) for transmitting a predetermined signal. For
example, when the number of symbols for transmitting a predetermined signal is a predetermined
number, the base station device 1 performs downlink communication in the initial connection
procedure using the first signal waveform. In other words, when using the first signal
waveform in downlink communication in the initial connection procedure, the base station
device 1 transmits a predetermined signal with a predetermined number of symbols.
After transmitting the predetermined signal, the base station device 1 uses the first
signal waveform in downlink communication in the initial connection procedure. If
the number of symbols for transmitting a predetermined signal is not the predetermined
number, the base station device 1 performs downlink communication in the initial connection
procedure using the second signal waveform. In other words, when using the second
signal waveform in downlink communication in the initial connection procedure, the
base station device 1 transmits a predetermined signal with a number of symbols other
than the predetermined number. After transmitting the predetermined signal, the base
station device 1 uses the second signal waveform in downlink communication in the
initial connection procedure. The predetermined signal itself is transmitted with
an arbitrary signal waveform or a predetermined signal waveform. In the description
of this paragraph, the first signal waveform and the second signal waveform may be
reversed.
[0195] The terminal device 2 controls reception processing used in downlink communication
in the initial connection procedure according to the number of symbols in which a
predetermined signal is received. For example, if the number of symbols in which a
predetermined signal is received is a predetermined value, the terminal device 2 uses
the reception processing for the first signal waveform to receive downlink communication
in the initial connection procedure. If the number of symbols in which the predetermined
signal is received is not the predetermined number, reception processing for the second
signal waveform is used to receive downlink communication in the initial connection
procedure. Note that the symbol is specified by a symbol index. In the description
of this paragraph, the first signal waveform and the second signal waveform may be
reversed.
[0196] Information regarding the number of symbols for transmitting a predetermined signal
may be notified from the base station device 1 to the terminal device 2 before transmitting
the predetermined signal or in a state of being included in the predetermined signal,
or such notification may be unnecessary. In this case, the terminal device 2 may detect
the number of symbols in which a predetermined signal is received from the received
predetermined signal. In this case, the base station device 1 does not need to explicitly
transmit information regarding the number of symbols in which a predetermined signal
is transmitted.
[0197] In the initial connection procedure and any subsequent time segment, the base station
device 1 may control the signal waveform to be used according to the time resources
(for example, symbols) or the number of symbols used each time downlink communication
is performed. The terminal device 2 may control reception processing applied to the
signal received from the base station device 1 according to the time resources (symbols)
or the number of symbols of the received signal. Accordingly, the base station device
1 and the terminal device 2 can selectively switch the signal waveform to be used
and reception processing each time downlink communication is performed.
[4]Information regarding non-orthogonal resources in which predetermined signal is
transmitted
[0198] Non-orthogonal resources are resources that may cause interference even if they are
different, and include multi-access resources (MA), multi-access physical resources
(MA), and the like.
[0199] The base station device 1 controls signal waveforms used in downlink communication
in the initial connection procedure, depending on non-orthogonal resources that transmit
predetermined signals. For example, when transmitting a predetermined signal using
a predetermined multi-access physical resource, the base station device 1 uses the
first signal waveform in downlink communication in the initial connection procedure.
In other words, when using the first signal waveform in downlink communication in
the initial connection procedure, the base station device 1 transmits a predetermined
signal using a predetermined multi-access physical resource. When transmitting a predetermined
signal using a multi-access physical resource other than the predetermined multi-access
physical resource, the base station device 1 uses the second signal waveform in downlink
communication in the initial connection procedure. In other words, when using the
second signal waveform in downlink communication in the initial connection procedure,
the base station device 1 transmits the predetermined signal using a multi-access
physical resource other than the predetermined multi-access physical resource. In
the description of this paragraph, the first signal waveform and the second signal
waveform may be reversed.
[0200] In the initial connection procedure, the terminal device 2 controls the reception
processing to be used according to the non-orthogonal resources including a predetermined
signal received from the base station device 1. For example, if the multi-access physical
resource that received the predetermined signal is the predetermined multi-access
physical resource, the terminal device 2 uses the reception processing for the first
signal waveform to receive the downlink of the initial connection procedure. If the
multi-access physical resource in which the predetermined signal has been received
is not the predetermined multi-access physical resource, downlink reception of the
initial connection procedure is performed using the reception processing for the second
signal waveform. In the description of this paragraph, the first signal waveform and
the second signal waveform may be reversed.
[0201] Information regarding the non-orthogonal resource in which a predetermined signal
is transmitted may be notified from the base station device 1 to the terminal device
2 before transmitting the predetermined signal or in a state of being included in
the predetermined signal, or such notification may be unnecessary. In this case, the
terminal device 2 may determine from the received predetermined signal whether the
non-orthogonal resource to which the predetermined signal was transmitted corresponds
to the predetermined multi-access physical resource. In this case, the base station
device 1 does not need to explicitly transmit information regarding the non-orthogonal
resource on which the predetermined signal is transmitted.
[0202] In the initial connection procedure or an arbitrary time segment thereafter, the
base station device 1 may selectively switch the signal waveform to be used depending
on the non-orthogonal resources to be used each time downlink communication is performed.
The terminal device 2 may switch the reception processing applied to the signal received
from the base station device 1 according to the non-orthogonal resources of the received
signal. Accordingly, the base station device 1 and the terminal device 2 can selectively
switch the signal waveform to be used and reception processing each time downlink
communication is performed.
[5]Information regarding number of transmission layers in downlink
[0203] The base station device 1 controls the signal waveform used for downlink signal transmission
according to the number of transmission layers. For example, when transmitting a predetermined
signal using the maximum number of transmission layers or two or more transmission
layers, the base station device 1 uses the first signal waveform in downlink communication
in the initial connection procedure. When transmitting a predetermined signal using
one transmission layer, the base station device 1 uses the second signal waveform
in downlink communication in the initial connection procedure.
[0204] The terminal device 2 controls reception processing used for downlink communication
in the initial connection procedure according to the number of transmission layers
of a predetermined signal received from the base station device 1. For example, if
the number of layers on which a predetermined signal is received is the maximum number
of transmission layers or two or more layers, the terminal device 2 receives downlink
communication using the reception processing for the first signal waveform in the
initial connection procedure. If the number of layers in which the predetermined signal
is received is 1, the terminal device 2 receives downlink communication using the
reception processing for the second signal waveform in the initial connection procedure.
In the description of this paragraph, the first signal waveform and the second signal
waveform may be reversed.
[0205] Information regarding the number of transmission layers in which a predetermined
signal is transmitted may be notified from the base station device 1 to the terminal
device 2 before transmitting the predetermined signal or in a state of being included
in the predetermined signal, or such notification may be unnecessary. In this case,
the terminal device 2 may determine the number of transmission layers in which the
predetermined signal has been transmitted from the received predetermined signal.
In this case, the base station device 1 does not need to explicitly transmit information
regarding the number of transmission layers in which a predetermined signal is transmitted.
A predetermined signal implicitly includes information on the number of transmission
layers.
[0206] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal, according to the number of transmission layers for transmitting the signal.
The terminal device 2 may switch the reception processing applied to the signal received
from the base station device 1 according to the number of transmission layers of the
received signal. Accordingly, the base station device 1 and the terminal device 2
can selectively switch the signal waveform to be used and reception processing each
time downlink communication is performed.
[6]Information regarding number of symbols included in slot
[0207] The base station device 1 controls the signal waveform to be used in downlink communication
according to the number of symbols included in a slot. For example, when the number
of symbols included in a slot for transmitting a predetermined signal is predetermined
(for example, 14), the base station device 1 uses the first signal waveform in downlink
communication in the initial connection procedure. If the number of symbols included
in the slot is different from the predetermined number, the base station device 1
uses the second signal waveform in downlink communication in the initial connection
procedure. In the description of this paragraph, the first signal waveform and the
second signal waveform may be reversed.
[0208] The terminal device 2 controls the reception processing to be used according to the
number of symbols included in the downlink slot. For example, if the number of symbols
included in a downlink slot in which a predetermined signal is transmitted is predetermined
(for example, 14), the terminal device 2 receives downlink communication using the
reception processing for the first signal waveform in the initial connection procedure.
If the number of symbols included in the downlink slot is different from the predetermined
number, the terminal device 2 receives the downlink communication using the reception
processing for the second signal waveform in the initial connection procedure. In
the description of this paragraph, the first signal waveform and the second signal
waveform may be reversed.
[0209] Information regarding the number of symbols included in a slot in which a predetermined
signal is transmitted may be notified from the base station device 1 to the terminal
device 2 before transmitting the predetermined signal or in a state of being included
in the predetermined signal, or such notification may be unnecessary. In this case,
the terminal device 2 may detect the number of symbols included in the slot from the
received predetermined signal. In this case, the base station device 1 does not need
to transmit information regarding the number of symbols included in the slot in which
a predetermined signal is transmitted.
[0210] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal according to the number of symbols included in the slot for transmitting the
signal. The terminal device 2 may switch the reception processing to be used for each
downlink slot according to the number of symbols included in the slot. Accordingly,
the base station device 1 and the terminal device 2 can selectively switch the signal
waveform to be used and reception processing each time downlink communication is performed.
[7]Information regarding subcarrier spacing
[0211] The base station device 1 controls the signal waveform to be used in downlink communication
according to the subcarrier spacing to be used. For example, when the subcarrier spacing
for transmitting a predetermined signal is equal to or greater than a predetermined
value, the base station device 1 uses the first signal waveform in downlink communication
in the initial connection procedure. When the subcarrier spacing for transmitting
a predetermined signal is less than the predetermined value, the base station device
1 uses the second signal waveform in downlink communication in the initial connection
procedure. In the description of this paragraph, the first signal waveform and the
second signal waveform may be reversed.
[0212] The terminal device 2 controls the reception processing to be used in the initial
connection procedure according to the subcarrier spacing of the signal received from
the base station device 1. For example, if the subcarrier spacing of a predetermined
signal received from the base station device 1 is equal to or greater than a predetermined
value, the terminal device 2 receives downlink communication using the reception processing
for the first signal waveform in the initial connection procedure. If the subcarrier
spacing of the predetermined signal received from the base station device 1 is less
than the predetermined value, the terminal device 2 receives downlink communication
using the reception processing for the second signal waveform in the initial connection
procedure. In the description of this paragraph, the first signal waveform and the
second signal waveform may be reversed.
[0213] Information regarding the subcarrier spacing in which a predetermined signal is transmitted
may be notified from the base station device 1 to the terminal device 2 before transmitting
the predetermined signal or in a state of being included in the predetermined signal,
or such notification may be unnecessary. In this case, the terminal device 2 may detect
the subcarrier spacing from the received predetermined signal. In this case, the base
station device 1 does not need to transmit information regarding the subcarrier spacing
in which a predetermined signal is transmitted.
[0214] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal according to the subcarrier spacing for transmitting the signal. The terminal
device 2 may switch reception processing for the received signal according to the
subcarrier spacing of the received signal. Accordingly, the base station device 1
and the terminal device 2 can selectively switch the signal waveform to be used and
reception processing each time downlink communication is performed.
[8]Information regarding communication channels used in downlink communication
[0215] The base station device 1 controls the signal waveform to be used in downlink communication
according to the communication channel in which the signal is transmitted. For example,
when transmitting a predetermined signal on the PBCH, the base station device 1 uses
the second signal waveform in downlink communication in the initial connection procedure.
When transmitting a predetermined signal using a communication channel other than
PBCH, the base station device 1 uses the first signal waveform in downlink communication
in the initial connection procedure. A second signal waveform may be used instead
of the first signal waveform. In the description of this paragraph, the first signal
waveform and the second signal waveform may be reversed.
[0216] In the initial connection procedure, the terminal device 2 controls the reception
processing to be used according to the communication channel for receiving the signal
from the base station device 1. For example, when receiving a predetermined signal
on the PBCH, the terminal device 2 receives downlink communication using the reception
processing for the second signal waveform in the initial connection procedure. When
receiving a predetermined signal on a communication channel other than PBCH, the terminal
device 2 receives downlink communication using the reception processing for the first
signal waveform in the initial connection procedure. When receiving on a communication
channel other than PBCH, reception processing for the second signal waveform may be
used instead of reception processing for the first signal waveform. In the description
of this paragraph, the first signal waveform and the second signal waveform may be
reversed.
[0217] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform to be used according to the
communication channel in which the signal is transmitted. For example, when transmitting
a signal on PBCH, the base station device 1 uses the second signal waveform for transmitting
the signal. When transmitting a signal on a communication channel other than PBCH,
the base station device 1 uses the first signal waveform (or second signal waveform).
The terminal device 2 may switch the reception processing to be used according to
the communication channel in which the signal is received. For example, when the terminal
device 2 receives a signal on the PBCH, the terminal device 2 receives the signal
using the reception processing for the second signal waveform. When the terminal device
2 receives the signal on a communication channel other than the PBCH, the terminal
device 2 receives the signal using the reception processing for the first signal waveform.
Accordingly, the base station device 1 and the terminal device 2 can selectively switch
the signal waveform to be used and reception processing each time downlink communication
is performed.
[9]Information regarding modulation methods used in downlink communication
[0218] The base station device 1 controls the signal waveform to be used in downlink communication
in the initial connection procedure according to the modulation method to be used.
For example, when transmitting a predetermined signal using a modulation method with
a modulation level of 16QAM or more (higher-order modulation method), the base station
device 1 uses the first signal waveform in downlink communication in the initial connection
procedure. When transmitting a predetermined signal using a modulation method (lower-order
modulation method) with a modulation level less than 16QAM, the base station device
1 uses the second signal waveform in downlink communication in the initial connection
procedure. Examples of lower-order modulation methods include BPSK and QPSK. In this
description, it is assumed that the same modulation method is applied to a signal
transmitted after a predetermined signal in the initial connection procedure. In the
description of this paragraph, the first signal waveform and the second signal waveform
may be reversed.
[0219] The terminal device 2 controls the reception processing to be used in the initial
connection procedure according to the modulation method applied to the signal received
from the base station device 1. For example, if a modulation method (higher-order
modulation method) with a modulation level of 16QAM or more is applied to a predetermined
signal received from the base station device 1, the terminal device 2 receives downlink
communication using the reception processing for the first signal waveform in the
initial connection procedure. If a modulation method (lower-order modulation method)
with a modulation level less than 16QAM is applied to the predetermined signal received
from the base station device 1, the terminal device 2 receives downlink communication
using the reception processing for the second signal waveform in the initial connection
procedure. In the description of this paragraph, the first signal waveform and the
second signal waveform may be reversed.
[0220] Information regarding the modulation method applied to a predetermined signal may
be notified from the base station device 1 to the terminal device 2 before transmitting
the predetermined signal or in a state of being included in the predetermined signal,
or such notification may be unnecessary. In this case, the terminal device 2 may detect
modulation method information from the received predetermined signal.
[0221] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal, according to the modulation method applied to the signal. The terminal device
2 may switch the reception processing used for the received signal according to the
modulation method applied to the received signal. Accordingly, the base station device
1 and the terminal device 2 can selectively switch the signal waveform to be used
and reception processing each time downlink communication is performed.
[10]Information regarding frequency bands used in downlink communication
[0222] The base station device 1 controls the signal waveform to be used in downlink communication
according to the frequency band used. For example, when transmitting a predetermined
signal using a band of 52.6 GHz or more, the base station device 1 uses the first
signal waveform in downlink communication in the initial connection procedure. When
transmitting a predetermined signal using a band less than 52.6 GHz, the base station
device 1 uses the second signal waveform in downlink communication in the initial
connection procedure. In the description of this paragraph, the first signal waveform
and the second signal waveform may be reversed.
[0223] In the initial connection procedure, the terminal device 2 controls reception processing
used for the received signal according to the frequency band of the received signal.
For example, when the terminal device 2 receives a predetermined signal in the downlink
from the base station device 1 in a band of 52.6 GHz or more, the terminal device
2 receives downlink communication using the reception processing for the first signal
waveform in the initial connection procedure. If a predetermined signal is received
in the band below 52.6 GHz in the downlink from the base station device 1, the terminal
device 2 receives downlink communication using the reception processing for the second
signal waveform in the initial connection procedure. In the description of this paragraph,
the first signal waveform and the second signal waveform may be reversed.
[0224] Information regarding the frequency band included in the slot in which a predetermined
signal is transmitted may be notified from the base station device 1 to the terminal
device 2 before transmitting the predetermined signal or in a state of being included
in the predetermined signal, or such notification may be unnecessary. In this case,
the terminal device 2 may detect the reception frequency band from the received predetermined
signal. In this case, the base station device 1 does not need to explicitly transmit
information regarding the frequency band in which the predetermined signal is transmitted.
[0225] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal, according to the frequency band used for transmitting the signal. The terminal
device 2 may switch the reception processing used for the received signal according
to the frequency band in which the signal is received. Accordingly, the base station
device 1 and the terminal device 2 can selectively switch the signal waveform to be
used and reception processing each time downlink communication is performed.
[11]Information regarding CP (cyclic prefix) length used in downlink communication
[0226] The base station device 1 controls the signal waveform to be used in downlink communication
according to the CP length to be used. For example, when transmitting a predetermined
signal using a CP length greater than or equal to a predetermined value, the base
station device 1 uses the first signal waveform in downlink communication in the initial
connection procedure. When transmitting a predetermined signal using a CP length less
than a predetermined value, the base station device 1 uses the second signal waveform
in downlink communication in the initial connection procedure. In this description,
it is assumed that the same CP length is used in the initial connection procedure
after transmitting a predetermined signal. In the description of this paragraph, the
first signal waveform and the second signal waveform may be reversed.
[0227] In the initial connection procedure, the terminal device 2 controls the reception
processing used for the received signal according to the CP length of the received
signal. For example, if the CP length of a predetermined signal received on the downlink
from the base station device 1 is equal to or greater than a predetermined value,
the terminal device 2 receives downlink communication using the reception processing
for the first signal waveform in the initial connection procedure. If the CP length
of the predetermined signal received in the downlink from the base station device
1 is less than the predetermined value, the terminal device 2 receives the downlink
communication using the reception processing for the second signal waveform in the
initial connection procedure. In the description of this paragraph, the first signal
waveform and the second signal waveform may be reversed.
[0228] During the initial connection procedure or an arbitrary time segment thereafter,
the base station device 1 may switch the signal waveform used for transmitting the
signal, according to the CP length used for transmitting the signal. The terminal
device 2 may switch the reception processing used for the received signal according
to the CP length of the received signal. Accordingly, the base station device 1 and
the terminal device 2 can selectively switch the signal waveform to be used and reception
processing each time downlink communication is performed.
[12]Information regarding DCI format
[0229] The base station device 1 controls signal waveforms used in downlink communication
according to the DCI format. For example, when Format A is used as the DCI format,
the base station device 1 uses the first signal waveform in the downlink communication
in the initial connection procedure or in another time segment. When Format B is used
as the DCI format, the base station device 1 uses the second signal waveform in the
downlink communication in the initial connection procedure or in another time segment.
In the description of this paragraph, the first signal waveform and the second signal
waveform may be reversed.
[0230] The terminal device 2 specifies the format of the DCI received from the base station
device 1, and if the format is A, performs reception processing for the first signal
waveform in the initial connection procedure or in another time segment. If the format
of the DCI received from the base station device 1 is Format B, the terminal device
2 performs reception processing for the second signal waveform in the initial connection
procedure or in another time segment. In the description of this paragraph, the first
signal waveform and the second signal waveform may be reversed.
[13]Explicit information regarding signal waveforms used in downlink communication
[0231] Information indicating that the first signal waveform is used (information A) and
information indicating that the second signal waveform is used (information B) are
defined. The base station device 1 transmits a signal including information A when
using the first signal waveform as the signal waveform to be used. After this, in
downlink communication, a signal may be transmitted using the first signal waveform
without including information A. The base station device 1 transmits a signal including
information B when using the second signal waveform as the signal waveform to be used.
After this, in downlink communication, a signal may be transmitted using the second
signal waveform without including information B.
[0232] When information A is included in the signal received from the base station device
1, the terminal device 2 uses the reception processing for the first signal waveform
for the received signal. Alternatively, the terminal device 2 may continue to use
the reception processing for the first signal waveform for signals received on the
downlink thereafter. When information B is included in the signal received from the
base station device 1, the terminal device 2 uses the reception processing for the
second signal waveform for the received signal. Alternatively, the terminal device
2 may continue to use the reception processing for the second signal waveform for
the signal received on the downlink thereafter.
[14]Information on whether predetermined signal is being transmitted
[0233] Whether a predetermined signal is being transmitted (whether a predetermined signal
is transmitted) itself functions as signal waveform identification information. That
is, the predetermined signal itself specifies which of the first signal waveform and
the second signal waveform is used. For example, when a certain synchronization signal
(referred to as synchronization signal A) means that a second signal waveform is used,
the base station device 1 transmits the synchronization signal A to notify the terminal
device 2 that the second signal waveform will be used in the initial connection procedure
or another time segment. In this case, after transmitting the synchronization signal
A, the base station device 1 uses the second signal waveform in downlink communication
in the initial connection procedure or in another time segment. The terminal device
2 performs reception processing for the first signal waveform until it receives the
synchronization signal A, and when it receives the synchronization signal A, switches
the reception processing to the reception processing for the second signal waveform.
In this example, an example is shown in which the first signal waveform is switched
to the second signal waveform. However, when switching the second signal waveform
to the first signal waveform, similar processing can be executed by defining the predetermined
signal to mean that the first signal waveform is to be used.
<Signal waveform switching notification>
[0234] It is assumed that the default signal waveform is determined to be either the first
signal waveform or the second signal waveform. When the base station device 1 switches
the signal waveform to be used in downlink communication from the default signal waveform
(one signal waveform) to the other signal waveform, the base station device 1 notifies
the terminal device 1 of information (second information) regarding switching of the
signal waveform to be used. Even when switching the signal waveform to be used from
another signal waveform to the default signal waveform, the base station device 1
notifies the terminal device 1 of information (second information) regarding the switching
of the signal waveform to be used.
[0235] For example, if the default signal waveform is a multi-carrier signal and the base
station device 1 determines that it is necessary to switch the signal waveform to
be used to a single-carrier signal, the base station device 1 notifies information
indicating the switching (second information). After switching the signal waveform
to be used to a single-carrier signal, when switching to a multi-carrier signal again,
the base station device transmits information indicating the switching again. The
switching information transmitted first and the switching information transmitted
later may be the same information or different information. As the switching information,
the signal waveform identification information according to any of the examples [1]to
[14]described above may be used. The switching information may be 1 bit.
[0236] As an operation on the receiving side, the terminal device 2 first performs reception
processing for a default signal waveform (here, a multi-carrier signal) on the signal
received from the base station device 1. Thereafter, when the terminal device 2 receives
the signal waveform identification information from the base station device 1, the
terminal device 2 switches the reception processing from the reception processing
for multi-carrier signals to the reception processing for single-carrier signals.
Furthermore, after that, when the terminal device 2 receives the signal waveform identification
information from the base station device 1, the terminal device 2 switches the reception
processing again from the reception processing for single-carrier signals to the reception
processing for multi-carrier signals.
<Example of switching signal waveform to be used according to communication processing
to be executed>
[0237] The base station device 1 controls signal waveforms to be used in downlink communication
according to communication processing to be executed. For example, the base station
device 1 uses a default signal waveform, that is, one of the first signal waveform
and the second signal waveform, as the signal waveform in downlink communication in
predetermined processing (first processing). In processing other than the predetermined
processing (second processing), the signal waveform to be used is switched to the
other of the first signal waveform and the second signal waveform. As an example,
the second signal waveform is a signal to which transform precoding is applied (for
example, a DFT-Spread-OFDM signal), and the first signal waveform is a signal to which
transform precoding is not applied (for example, an OFDM signal).
[0238] The terminal device 2 switches the reception processing to be used according to the
communication processing to be executed. When the terminal device 2 performs the first
processing with the base station device 1, the terminal device 2 sets reception processing
for the default signal waveform. When the terminal device 2 performs the second processing
with the base station device 1, the terminal device 2 sets reception processing for
the other signal waveform. Specifically, the signal waveform switch 301 of the terminal
device 2 provides the signal received on the downlink from the base station device
1 to one of the first signal waveform receiver 303 and the second signal waveform
receiver 305 according to the communication processing to be executed. In the case
of the first processing, the signal received on the downlink from the base station
device 1 is provided to the signal waveform receiver corresponding to the default
signal waveform. In the case of the second processing, the signal received on the
downlink from the base station device 1 is provided to the other signal waveform receiver.
The terminal device 2 may autonomously detect information regarding the communication
processing to be executed without being notified from the base station device 1.
[0239] An example of the predetermined processing will be shown below.
- Synchronization signal transmission/reception processing (transmission/reception processing
of synchronization signals such as PSS, SSS, TSS)
- Random access transmission/reception processing (message 2 transmission/reception
processing, message 4 transmission/reception processing, message B transmission/reception
processing)
- Control signal transmission/reception processing (for example, PDCCH transmission/reception
processing)
- Reference signal transmission/reception processing
<Example of determining application timing or application period of signal waveform>
[0240] The base station device 1 may set a start timing and/or an application period for
applying any signal waveform (target signal waveform).
[0241] For example, when switching the signal waveform to be used from a first signal waveform
to a second signal waveform, the base station device 1 sets the start timing and/or
application period for applying the second signal waveform (target signal waveform).
The base station device 1 notifies the terminal device 2 of information regarding
the start timing of applying the second signal waveform (third information) and/or
information regarding the application period (fourth information).
[0242] An example of the information indicating the start timing (third information) is
information for specifying a slot (application start slot) in which application of
the target signal waveform is started. The information may be information specifying
a slot (for example, the immediately previous slot) a predetermined number of times
before the application start slot, or information specifying the application start
slot. In the former case, the second signal waveform is used from a slot a predetermined
number of times after the designated slot. In the latter case, the second signal waveform
is used from the designated slot. In the base station device 1 and/or the terminal
device 2, the start timing of the second signal waveform may be managed by an arbitrary
method. For example, the start timing may be managed by a timer or by a time (absolute
time) corresponding to the start timing. Alternatively, the start timing may be managed
by the number of time units (number of symbols, number of slots, and the like) until
the start timing.
[0243] The information (fourth information) for specifying the application period of the
second signal waveform (target signal waveform) may be the time length in which the
second signal waveform is applied, or may be the end time indicating the end of the
application period, or may be the number of time units such as the number of symbols
or the number of slots. The application period is managed in the base station device
1 and/or the terminal device 2 in an arbitrary manner depending on each type of information.
For example, the application period may be managed by a timer, an end time, or a number
of time units (number of symbols, number of slots, and the like).
[0244] The base station device 1 uses the second signal waveform (target signal waveform)
in downlink communication during the application period of the second signal waveform
(target signal waveform). When the application period has elapsed, the base station
device 1 switches the signal waveform to be used in downlink communication to the
first signal waveform.
[0245] The application period or the length of the application period of the target signal
waveform may be statically determined based on specifications or the like. Alternatively,
the base station device 1 may semi-statically set the application period or the length
of the application period of the target signal waveform using SI (System Information)
or RRC signaling. Alternatively, the application period or the length of the application
period of the target signal waveform may be dynamically set using MAC CE or DCI.
[0246] In addition, the setting of the application period or the length of the application
period of the target signal waveform may be performed for each of multiple signal
waveforms if each can be the target signal waveform. If only one of them can be the
target signal waveform, it may be set only for that one signal waveform.
[0247] When temporarily switching from the default signal waveform to another signal waveform
(target signal waveform), the base station device 1 may set the start timing and/or
application period of the target signal waveform.
<Handover>
[0248] When a terminal device performs a handover, the source base station device may transmit
information regarding a signal waveform used by the target base station device to
the terminal device in advance. In order to transmit information regarding the signal
waveform, the source base station device can use a handover command such as RRC reconfiguration.
The terminal device performs an initial connection procedure with the target base
station device (cell) based on the information received from the source base station
device. The target base station device may notify the source base station device of
information regarding the signal waveform to be used, and the source base station
device may notify the terminal device of information regarding the signal waveform
used by the target base station device based on the notified information. The information
transmitted to the terminal device may be information regarding the signal waveform
of the synchronization signal to be first received from the target base station device.
Alternatively, the information transmitted to the terminal device may be information
regarding the signal waveform of a specific signal (for example, a signal on a specific
channel) transmitted from the target base station device. In this case, the target
base station device may omit the processing of transmitting signal waveform identification
information of a signal waveform used for a specific signal to the terminal device.
<Selective use of signal waveforms according to area>
[0249] The base station device 1 may control the signal waveform to be used in downlink
communication with the terminal device 2 depending on whether the terminal device
2 is located in an edge area of a cell provided by the base station device 1 or an
area other than the cell edge area. For example, a single-carrier signal is considered
to be more suitable than a multi-carrier signal in a cell edge area where it requires
transmission with higher power than areas other than the edge area. Therefore, the
base station device 1 may use, for example, a single-carrier signal for a cell edge
area, and a multi-carrier signal for areas other than the edge area.
<Selective use of signal waveforms according to elevation angle of satellite relative
to terminal device>
[0250] When the base station device 1 is a satellite, the base station device 1 may determine
the signal waveform to be used in downlink communication with the terminal device
2 according to the elevation angle with respect to the terminal device 2. For example,
when the elevation angle is low, transmission with higher power is required than when
the elevation angle is high. For this reason, single-carrier signals are considered
to be more suitable than multi-carrier signals. Therefore, the base station device
1 may determine a single-carrier signal when the elevation angle with respect to the
terminal device 2 is less than a threshold, and a multi-carrier signal when it is
greater than or equal to the threshold as the signal waveform to be used for the terminal
device 2.
[0251] <Selective use of signal waveforms according to altitude of satellite>
[0252] When the base station device 1 is a satellite, the base station device 1 may determine
the signal waveform to be used in downlink communication with the terminal device
2 according to the altitude of the base station device 1. For example, when the satellite
is at a high altitude, higher power transmission is required than when the satellite
is at a lower altitude. For this reason, single-carrier signals are considered to
be more suitable than multi-carrier signals. Therefore, the base station device 1
may determine a single-carrier signal when the altitude of the subject station (satellite)
is equal to or greater than a threshold, and a multi-carrier signal when it is below
the threshold as the signal waveform to be used for the terminal device 2. Alternatively,
the signal waveform may be determined depending on whether the base station device
1 is a non-ground station such as a satellite or a terrestrial base station.
<Selective use of signal waveforms according to satellite performance>
[0253] When the base station device 1 is a satellite, the base station device 1 may determine
the signal waveform used for downlink communication with the terminal device 2 according
to the performance or type of the subject station (satellite). For example, in the
case of a satellite that cannot transmit with high power (such as a low-cost satellite),
a single-carrier signal may be more suitable than a multi-carrier signal. Therefore,
for example, the base station device 1 determines a single-carrier signal when the
subject station is unable to transmit with high power and can transmit with low power,
which is smaller than the high power, and a multi-carrier signal when its optical
switch function station can transmit with high power, as the signal waveform to be
used for the terminal device 2. High power is power above a threshold, and low power
is power below a threshold.
<Other selective use of signal waveforms>
[0254] The base station device 1 performs control to measure the difference between the
desired uplink reception timing and the actual reception timing for the terminal device
2, and adjusts the transmission timing of the terminal device 2 so as to shift the
uplink transmission timing by the measured difference. The base station device 1 may
be a device such as a satellite that may be located at a long distance from the terminal
device 2. The base station device 1 transmits information regarding a transmission
timing offset or timing advance to the terminal device 2 as information regarding
the transmission timing of the terminal device 2. The terminal device 2 adjusts the
uplink transmission timing based on the information received from the base station
device 1.
[0255] If the measured difference is greater than or equal to the threshold, in other words,
if the transmission timing offset or timing advance is greater than or equal to the
threshold, it is considered that the base station device 1 and the terminal device
2 are located at a long distance from each other. In this case, a single-carrier signal
(second signal waveform) is considered more suitable than a multi-carrier signal (first
signal waveform).
[0256] Therefore, if the measured difference is greater than or equal to the threshold,
in other words, if the transmission timing offset or timing advance is greater than
or equal to the threshold, the base station device 1 may determine a single-carrier
signal as the signal waveform to be used for transmission to the terminal device 2.
If the measured difference is less than the threshold, in other words, if the transmission
timing offset or timing advance is less than the threshold, the base station device
1 may determine a multi-carrier signal as the signal waveform to be used for transmission
to the terminal device 2. The terminal device 2 acquires information regarding transmission
timing from the base station device 1. Based on the acquired information, the terminal
device 2 sets reception processing for the second signal waveform if the transmission
timing offset or timing advance is greater than or equal to the threshold, and sets
reception processing for the first signal waveform if it is less than the threshold.
In this way, the signal waveform switch 301 of the terminal device 2 determines the
signal waveform receiver that provides a signal to be received from the base station
device 1 from among the first signal waveform receiver 303 and the second signal waveform
receiver 305 based on the acquired information. The signal waveform switch 301 of
the terminal device 2 provides the signal received from the base station device 1
to the determined signal waveform receiver.
<Increase in communication speed or capacity in downlink single-carrier transmission>
[0257] As described at the beginning of the description of the present embodiment, when
carrying out single-carrier transmission on the uplink, it is necessary to allocate
contiguous resources in the frequency domain in order to suppress an increase in PAPR.
[0258] Fig. 20 shows an example of contiguous resource allocation in the frequency domain
when a terminal device performs single-carrier transmission (transmits a single-carrier
signal) on the uplink. Transform precoding (IDFT or FFT, and the like) is performed
on the uplink signal (signals A
0 to A
3 in the figure) of the terminal device (terminal device A in the figure), and the
precoded signals A'
0 to A'
3 are allocated to contiguous resources in the frequency domain. Bands other than the
allocated resources are uplink bands for other terminal devices. Terminal device A
performs OFDM processing (IDFT, IFFT, and the like) on signals A'
0 to A'
3 allocated to resources, and generates a single-carrier signal.
[0259] Fig. 21 shows an example of discontiguous resource allocation in the frequency domain
when terminal device A performs single-carrier transmission on the uplink. Terminal
device A allocates precoded signals A'
0 to A'
3 to discontiguous resources in the frequency domain. In this case, there is a problem
that PAPR increases.
[0260] The present embodiment proposes a method for suppressing an increase in PAPR even
if signals addressed to a terminal device are allocated to discontiguous resources
in the frequency domain when the base station device 1 performs single-carrier transmission
in downlink communication. A specific example of this method is shown below.
[0261] Fig. 22 shows a configuration example of the second signal waveform transmitter in
the radio transmitter of the base station device 1.
[0262] Processing to combine signals (A
0 to A
3) addressed to terminal device A, signals addressed (B
0 to B
3) to terminal device B, and signals (C
0 to C
3) addressed to terminal device C is performed as preprocessing for transform precoding.
This processing is referred to as mapping, but the name is not limited to this. In
this example, the signals are mapped in the order of A
0 to A
3, B
0 to B
3, and C
0 to C
3, but this order is just an example, and other orders may be used.
[0263] A signal sequence (combined signal) obtained by the mapping is subjected to transform
precoding. The precoded signals X'
0 to X'
11 are allocated to contiguous resources in the frequency domain. The base station device
1 performs OFDM processing (IDFT, IFFT, and the like) on the signals X'
0 to X'n allocated to the resources, and generates a single-carrier signal. As a result,
contiguous allocation of resources in the frequency domain is performed, so an increase
in PAPR can be suppressed.
[0264] Each terminal device that receives a single-carrier signal may extract signals addressed
to the subject terminal device from a signal sequence after transform de-precoding
(including signals addressed to multiple terminal devices) based on the mapping information
in the single-carrier signal reception processing. Accordingly, each terminal device
can acquire a signal addressed to the subject terminal device from a single-carrier
signal that includes signals addressed to a plurality of terminal devices.
[0265] The mapping information of each terminal device (information for identifying the
position of the signal addressed to each terminal device in the signal sequence) may
be transmitted by the base station device 1 to each terminal device in advance, or
may be determined in advance based on the specifications and the like, or may be obtained
by each terminal device using other methods.
[0266] Mapping information for each terminal device may be associated with resource allocation
information for each terminal device. In this case, the position of the signal addressed
to each terminal device in the serial signal can be determined from the allocated
resources of each terminal device. The resource allocation information may represent
frequency resource allocation for each terminal device in multi-carrier transmission.
[0267] Fig. 23 shows another example of the configuration of the second signal waveform
transmitter in the radio transmitter of the base station device 1. In addition to
signals (A
0 to A
3) addressed to terminal device A, signals (B
0 to B
3) addressed to terminal device B, and signals (Co to C
3) addressed to terminal device C, known signals (D
0 to D
1) are also mapped. The known signal is a broadcast signal that includes information
that is commonly notified to a plurality of terminal devices. The known signal may
include mapping information for each terminal device.
[0268] In this case, each terminal device can identify the position of the signal addressed
to the subject terminal device in the signal sequence from the known signal and acquire
the signal addressed to the subject terminal device. The position information of the
known signal in the signal sequence may be transmitted from the base station device
1 to each terminal device in advance, may be determined in advance based on specifications
and the like, or may be acquired by each terminal device using other methods.
[0269] Fig. 24 shows still another configuration example of the second signal waveform transmitter
in the radio transmitter of the base station device 1. In the configurations shown
in Figs. 22 and 23, signals addressed to all terminal devices are transform-precoded
together, but in the configuration shown in Fig. 24, signals addressed to each terminal
device are transform-precoded for each terminal device. After transform precoding
is performed for each terminal device, precoded signals of a plurality of terminal
devices are mapped onto contiguous frequency resources. In the illustrated example,
signals for terminal device A, terminal device B, and terminal device C are transform-precoded
for each terminal device.
[0270] As a modification, a signal for one terminal device and each known signal may be
individually transform-precoded. For example, a signal for terminal device A and a
known signal are individually transform-precoded. The precoded signal of terminal
device A and the precoded signal of the known signal are mapped onto contiguous frequency
resources.
[0271] Fig. 25 shows still another configuration example of the second signal waveform transmitter
in the radio transmitter of the base station device 1. In Fig. 24, the precoded signals
of each terminal device are mapped to contiguous frequency resources without changing
the order between the terminal devices, but in the configuration of Fig. 25, the order
of the precoded signals is changed between the terminal devices. Precoded signals
of a plurality of terminal devices are combined, the order of the combined signals
is changed, and the changed signals are mapped to contiguous frequency resources.
At this time, the precoded signals of at least one terminal device among the plurality
of terminal devices are mapped to non-contiguous resources in the frequency domain.
The order of the signals of each terminal device may be changed depending on the channel
response of each terminal device. As an example, the order of signals may be changed
so that the signals of the terminal device can be allocated to frequency resources
with good channel conditions for each terminal device. Specifically, for example,
the order of signals may be changed so that the channel quality of each terminal device
is above a certain value, or the order of signals may be changed so that the average
channel quality of multiple terminal devices is above a certain value, or the order
of signals may be changed based on other criteria. This processing may be included
in the frequency resource mapping processing, or may be performed as separate processing.
The configuration for changing the order of signals is similarly applicable to the
base station device shown in Fig. 22 or 23.
[0272] In the configurations shown in Figs. 22 to 25, it is desirable that the signal addressed
to each terminal device be a signal modulated using the modulation method of the order
as low as possible in order to reduce PAPR. If the modulation method of the signal
addressed to terminal device A is QAM modulation with a high modulation level (for
example, 16QAM), the PAPR tends to increase. PAPR can be reduced by using a lower-order
modulation method with a low modulation level, such as BPSK, QPSK, or PSK, as the
modulation method for all signals addressed to terminal device A, terminal device
B, and terminal device C. In particular, PSK is a modulation method that does not
contain information in amplitude, and a method using PSK can be considered as an example.
For example, instead of 4PSK (QPSK), 16QAM, and 64QAM used in multi-carrier transmission,
4PSK, 8PSK, 16PSK, 32PSK, and the like are used in single-carrier transmission.
[0273] From the same point of view, it is desirable that the known signal shown in Fig.
23 is modulated using a lower-order modulation method such as BPSK, QPSK, or PSK.
Alternatively, it is also possible to reduce PAPR by using a specific complex signal
point as a known signal, such as using complex signal point (I, Q) = (+1, 0) as a
known signal. Here, the complex signal points may also be referred to as complex-valued
modulation symbols.
[0274] Regarding transform precoding, in the case of uplink, transform precoding (DFT)
is generally performed by applying a DFT size corresponding to the frequency resources
of the terminal device. On the other hand, in the present embodiment, in the case
of downlink, in addition to applying the DFT size corresponding to the frequency resource
of each terminal device (see Figs. 24 and 25), execution of transform precoding (FFT)
using the FFT size is also applied. That is, as shown in Fig. 22 or 23, it is possible
to use FFT by transform-precoding a combination of signals of a plurality of terminal
devices. In this case, there is an advantage that the base station and the terminal
device do not need to perform DFT according to the size of the frequency resource.
Furthermore, since information can be reflected on all frequency resources by FFT,
it is possible to obtain a frequency diversity effect.
<FFT/IFFT size and DFT/IDFT size>
[0275] In the present embodiment, the FFT/IFFT size may represent any one of the following.
Note that * represents multiplication.
- Power of 2
- (The size of the resource grid) * (Number of subcarriers per resource block)
[0276] In the present embodiment, the DFT/IDFT size may represent the following.
- Scheduled bandwidth for uplink or downlink transmission, expressed as a number of
subcarriers
- (Scheduled bandwidth for uplink transmission, expressed as a number of resource blocks)
* (Number of subcarriers per resource block)
- Size that satisfies 2a*3b*5c (a, b, c are positive integers)
<Signaling>
[0277] In the present embodiment, the following signaling information may be transmitted
from the base station device to the terminal device.
- Types of transform precoding
[0278] The base station device may transmit information that can specify the type of transform
precoding to the terminal device. The terminal device specifies the type of transform
precoding performed by the base station device based on the received information,
and performs reception processing according to the specified type. For example, if
it is specified from the received information that the size of transform precoding
is FFT size, it can be determined that transform precoding is performed by the base
station after combining the signals of multiple terminal devices (see Fig. 22 or 23).
The terminal device performs reception processing according to the determination result.
On the other hand, if the terminal device specifies from the received information
that the transform precoding size is the DFT size corresponding to the frequency resource,
it can be determined that transform precoding is performed by the base station device
for each signal of each terminal device (see Fig. 24 or 25). The terminal device performs
reception processing according to the determination result. That is, the terminal
device can switch between the reception processing corresponding to the base station
configuration of Fig. 22 or 23 and the reception processing corresponding to the base
station configuration of Fig. 24 or 25.
- Information regarding known signals
[0279] The base station device may transmit complex signal point information of the known
signal to the terminal device. The terminal device may decode the known signal based
on the received information. In addition, the base station device may transmit information
regarding whether a known signal is inserted (see Fig. 23). If a known signal is inserted,
the terminal device may determine that the known signal has been inserted into a resource
other than the resource allocated to the terminal device. If it is not inserted, the
terminal device may determine that a signal to another terminal device has been transmitted.
For example, as a modification of the configuration in Fig. 24, known signals are
used instead of terminal device B and terminal device C. When the terminal device
A determines that a known signal has been inserted, the terminal device A determines
that a known signal has been inserted into a resource other than the resource allocated
to the terminal device itself, and decodes the known signal. If the terminal device
A determines that a known signal has not been inserted, the terminal device A determines
that a signal for another terminal device has been inserted into a resource other
than the resource allocated to the subject terminal device.
[0280] As described above, according to the present embodiment, when supporting both multi-carrier
transmission and single-carrier transmission, it is possible to satisfy the requirement
for low PAPR in downlink communication regardless of the operating frequency band.
Furthermore, according to the present embodiment, even if the resource allocation
of signals addressed to a specific terminal device is not contiguous in the frequency
domain, the overall resource allocation of signals addressed to individual terminal
devices is contiguous in the frequency domain. Thus, it is possible to allocate discontiguous
resources in the frequency domain while suppressing an increase in PAPR. In this way,
resources can be allocated more flexibly and the speed and capacity of downlink communication
can be further increased.
[0281] It should be noted that the above-described embodiments show examples of embodying
the present disclosure, and the present disclosure can be implemented in various other
forms. For example, various modifications, substitutions, omissions, or combinations
thereof are possible without departing from the gist of the present disclosure. Forms
with such a modification, substitution, omission, or the like are also included in
the scope of the invention described in the claims and their equivalents, as well
as being included in the scope of the present disclosure.
[0282] In addition, the effects of the present disclosure described herein are merely exemplary
and may have other effects.
[0283] Note that the present disclosure can also have the following configuration.
[Item 1]
[0284] Abase station device comprising:
a controller configured to:
notify a terminal device of first information regarding a signal waveform to be used
in downlink communication in an initial connection procedure performed with the terminal
device among a first signal waveform and a second signal waveform; and
perform the downlink communication in the initial connection procedure with the signal
waveform to be used based on the first information.
[Item 2]
[0285] The base station device according to item 1, wherein
the first signal waveform includes a multi-carrier signal, and the second signal waveform
includes a single-carrier signal.
[Item 3]
[0286] The base station device according to item 1 or 2, further comprising:
a first signal waveform transmitter that generates the first signal waveform and transmits
the first signal waveform; and
a second signal waveform transmitter that generates the second signal waveform and
transmits the second signal waveform, wherein
the second signal waveform transmitter generates the second signal waveform using
transform precoding, and
the first signal waveform transmitter generates the first signal waveform without
using the transform precoding.
[Item 4]
[0287] The base station device according to item 3, wherein
the second signal waveform transmitter combines signals addressed to a plurality of
the terminal devices and performs the transform precoding on the combined signals.
[Item 5]
[0288] The base station device according to item 3 or 4, wherein
the second signal waveform transmitter combines signals addressed to one or a plurality
of the terminal devices and a broadcast signal, and performs the transform precoding
on the combined signals.
[Item 6]
[0289] The base station device according to any one of items 3 to 5, wherein
the second signal waveform transmitter performs the transform precoding on signals
addressed to the plurality of terminal devices for each terminal device, and maps
the transform-precoded signals of the plurality of terminal devices onto contiguous
resources in a frequency domain.
[Item 7]
[0290] The base station device according to item 6, wherein
the second signal waveform transmitter maps the transform-precoded signals of at least
one terminal device among the plurality of terminal devices onto non-contiguous resources
in the frequency domain.
[Item 8]
[0291] The base station device according to any one of items 1 to 7, wherein
the first information includes information regarding the number of transmission layers
used in the downlink communication.
[Item 9]
[0292] The base station device according to any one of items 1 to 8, wherein
the controller performs downlink communication with the terminal device using one
of the first signal waveform and the second signal waveform, and when switching the
one signal waveform to the other of the first signal waveform and the second signal
waveform, the controller notifies the terminal device of second information regarding
switching of the signal waveform.
[Item 10]
[0293] The base station device according to any one of items 1 to 9, wherein
when switching the signal waveform to be used from one of the first signal waveform
and the second signal waveform to the other, the controller notifies the terminal
device of third information regarding a start timing of using the other signal waveform,
and
based on the third information, the controller switches the signal waveform to be
used to the other signal waveform at the start timing.
[Item 11]
[0294] The base station device according to any one of items 1 to 10, wherein
when switching the signal waveform to be used from one of the first signal waveform
and the second signal waveform to the other, the controller notifies the terminal
device of fourth information regarding a period in which the other signal waveform
is used, and
based on the fourth information, the controller perform downlink communication with
the terminal device based on the other signal waveform during at least a part of the
period.
[Item 12]
[0295] The base station device according to item 11, wherein
after the period has elapsed, the controller switches the signal waveform used for
downlink communication with the terminal device from the other signal waveform to
the one signal waveform.
[Item 13]
[0296] The base station device according to any one of items 1 to 12, wherein
the controller determines one of the first signal waveform and the second signal waveform
as a signal waveform to be used for downlink communication with the terminal device
according to at least one of altitude and performance of the base station device,
and performs the downlink communication with the terminal device using the one signal
waveform.
[Item 14]
[0297] A terminal device comprising:
a controller configured to:
acquire first information regarding a signal waveform to be used in downlink communication
in an initial connection procedure performed with a base station device among a first
signal waveform and a second signal waveform; and
perform the downlink communication in the initial connection procedure based on the
first information.
[Item 15]
[0298] The terminal device according to item 14, wherein
the first signal waveform includes a multi-carrier signal, and the second signal waveform
includes a single-carrier signal.
[Item 16]
[0299] The terminal device according to item 14 or 15, wherein
the first signal waveform is a signal generated using transform precoding, and the
second signal waveform is a signal generated without using the transform precoding.
[Item 17]
[0300] The terminal device according to item 15 or 16, further comprising:
a first signal waveform receiver that performs reception processing of the first signal
waveform;
a second signal waveform receiver that performs reception processing of the second
signal waveform; and
a signal waveform switch configured to:
when performing first processing with the base station device, provide a signal received
on downlink from the base station device to one of the first signal waveform receiver
and the second signal waveform receiver; and
when performing second processing different from the first processing with the base
station device, provide
the signal received on downlink from the base station device to the other of the first
signal waveform receiver and the second signal waveform receiver.
[Item 18]
[0301] The terminal device according to item 17, wherein
the first processing includes at least one of:
synchronization signal transmission/reception processing;
transmission/reception processing of at least one of message 2, message 4 and message
B in a random access procedure;
control signal transmission/reception processing; and
reference signal transmission/reception processing.
[Item 19]
[0302] The terminal device according to item 17 or 18, further comprising:
a first signal waveform receiver that performs reception processing of the first signal
waveform;
a second signal waveform receiver that performs reception processing of the second
signal waveform; and
a signal waveform switch that provides a signal received on downlink from the base
station device to one of the first signal waveform receiver and the second signal
waveform receiver, wherein
the controller acquires information regarding transmission timing of uplink communication
to the base station device, and
the signal waveform switch determines a signal waveform receiver that provides the
received signal from among the first signal waveform receiver and the second signal
waveform receiver based on the information regarding the transmission timing.
[Item 20]
[0303] A radio communication system comprising a base station device and a terminal device,
wherein
the base station device includes a first controller configured to notify the terminal
device of first information regarding a signal waveform to be used in downlink communication
in an initial connection procedure performed with the terminal device among a first
signal waveform and a second signal waveform and perform the downlink communication
in the initial connection procedure with the signal waveform to be used based on the
first information, and
the terminal device includes a second controller configured to acquire the first information
from the base station device and perform the downlink communication in the initial
connection procedure based on the first information.
[Reference Signs List]
[0304]
- 1
- Base station device
- 2
- Terminal device
- 2A
- Terminal device
- 2B
- Terminal device
- 3
- Relay device (relay station)
- 4
- Terrestrial network
- 11
- Geostationary satellite
- 12
- Low-earth-orbiting satellite
- 13
- Aviation station device
- 15
- Core network
- 16
- Internet
- 17
- Macro cell
- 18
- Femto cell
- 19
- Airborne platform
- 101
- Upper-layer processor
- 103
- Controller
- 105
- Receiver
- 107
- Transmitter
- 109
- Antenna
- 201
- Upper-layer processor
- 203
- Controller
- 205
- Receiver
- 207
- Transmitter
- 209
- Antenna
- 301
- Signal waveform switch
- 303
- First signal waveform receiver
- 305
- Second signal waveform receiver
- 401
- Signal waveform switch
- 403
- First signal waveform transmitter
- 405
- Second signal waveform transmitter
- 1051
- Decoder
- 1053
- Demodulator
- 1055
- Demultiplexer
- 1057
- Radio receiver
- 1059
- Channel measurement unit
- 1071
- Encoder
- 1073
- Modulator
- 1075
- Multiplexer
- 1077
- Radio transmitter
- 1079
- Link reference signal generator
- 2051
- Decoder
- 2053
- Demodulator
- 2055
- Demultiplexer
- 2057
- Radio receiver
- 2059
- Channel measurement unit
- 2071
- Encoder
- 2073
- Modulator
- 2075
- Multiplexer
- 2077
- Radio transmitter
- 2079
- Link reference signal generator
- 3031
- CP remover
- 3033
- S/P unit
- 3035
- DFT unit
- 3037
- P/S unit
- 3051
- CP remover
- 3053
- S/P unit
- 3055
- DFT unit
- 3057
- IDFT unit
- 4031
- S/P unit
- 4033
- IDFT unit
- 4035
- P/S unit
- 4037
- CP inserter
- 4051
- DFT unit
- 4053
- IDFT unit
- 4055
- P/S unit
- 4057
- CP inserter